Storing raid data as encoded data slices in a dispersed storage network

ABSTRACT

A method begins by a processing module receiving data for storage and interpreting the data to identify the data as redundant array of independent disks (RAID) data. The method continues with the processing module interpreting the RAID data to identify at least one of RAID block data and RAID parity data. When the RAID data includes RAID block data and RAID parity data the method continues with the processing module encoding the RAID block data in accordance with error coding dispersal storage function parameters to produce at least one set of encoded data slices and outputting the at least one set of encoded data slices to a dispersed storage network memory.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility patent application claims priority pursuant to35 U.S.C. §120 as a continuation of U.S. Utility application Ser. No.12/983,226, entitled “STORING RAID DATA AS ENCODED DATA SLICES IN ADISPERSED STORAGE NETWORK”, filed Dec. 31, 2010, which claims prioritypursuant to 35 U.S.C. §119(e) to U.S. Provisional Application No.61/308,938, entitled “MULTIPLE MEMORY TYPE STORAGE SYSTEM”, filed Feb.27, 2010 and U.S. Provisional Application No. 61/314,166, entitled“STORAGE AND RETRIEVAL IN A DISTRIBUTED STORAGE SYSTEM”, filed Mar. 16,2010, all of which are hereby incorporated herein by reference in theirentirety and made part of the present U.S. Utility patent applicationfor all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention relates generally to computing systems and moreparticularly to data storage solutions within such computing systems.

2. Description of Related Art

Computers are known to communicate, process, and store data. Suchcomputers range from wireless smart phones to data centers that supportmillions of web searches, stock trades, or on-line purchases every day.In general, a computing system generates data and/or manipulates datafrom one form into another. For instance, an image sensor of thecomputing system generates raw picture data and, using an imagecompression program (e.g., JPEG, MPEG, etc.), the computing systemmanipulates the raw picture data into a standardized compressed image.

With continued advances in processing speed and communication speed,computers are capable of processing real time multimedia data forapplications ranging from simple voice communications to streaming highdefinition video. As such, general-purpose information appliances arereplacing purpose-built communications devices (e.g., a telephone). Forexample, smart phones can support telephony communications but they arealso capable of text messaging and accessing the internet to performfunctions including email, web browsing, remote applications access, andmedia communications (e.g., telephony voice, image transfer, musicfiles, video files, real time video streaming. etc.).

Each type of computer is constructed and operates in accordance with oneor more communication, processing, and storage standards. As a result ofstandardization and with advances in technology, more and moreinformation content is being converted into digital formats. Forexample, more digital cameras are now being sold than film cameras, thusproducing more digital pictures. As another example, web-basedprogramming is becoming an alternative to over the air televisionbroadcasts and/or cable broadcasts. As further examples, papers, books,video entertainment, home video, etc. are now being stored digitally,which increases the demand on the storage function of computers.

A typical computer storage system includes one or more memory devicesaligned with the needs of the various operational aspects of thecomputer's processing and communication functions. Generally, theimmediacy of access dictates what type of memory device is used. Forexample, random access memory (RAM) memory can be accessed in any randomorder with a constant response time, thus it is typically used for cachememory and main memory. By contrast, memory device technologies thatrequire physical movement such as magnetic disks, tapes, and opticaldiscs, have a variable response time as the physical movement can takelonger than the data transfer, thus they are typically used forsecondary memory (e.g., hard drive, backup memory, etc.).

A computer's storage system will be compliant with one or more computerstorage standards that include, but are not limited to, network filesystem (NFS), flash file system (FFS), disk file system (DFS), smallcomputer system interface (SCSI), internet small computer systeminterface (iSCSI), file transfer protocol (FTP), and web-baseddistributed authoring and versioning (WebDAV). These standards specifythe data storage format (e.g., files, data objects, data blocks,directories, etc.) and interfacing between the computer's processingfunction and its storage system, which is a primary function of thecomputer's memory controller.

Despite the standardization of the computer and its storage system,memory devices fail; especially commercial grade memory devices thatutilize technologies incorporating physical movement (e.g., a discdrive). For example, it is fairly common for a disc drive to routinelysuffer from bit level corruption and to completely fail after threeyears of use. One solution is to use a higher-grade disc drive, whichadds significant cost to a computer.

Another solution is to utilize multiple levels of redundant disc drivesto replicate the data into two or more copies. One such redundant driveapproach is called redundant array of independent discs (RAID). In aRAID device, a RAID controller adds parity data to the original databefore storing it across the array. The parity data is calculated fromthe original data such that the failure of a disc will not result in theloss of the original data. For example, RAID 5 uses three discs toprotect data from the failure of a single disc. The parity data, andassociated redundancy overhead data, reduces the storage capacity ofthree independent discs by one third (e.g., n−1=capacity). RAID 6 canrecover from a loss of two discs and requires a minimum of four discswith a storage capacity of n−2.

While RAID addresses the memory device failure issue, it is not withoutits own failures issues that affect its effectiveness, efficiency andsecurity. For instance, as more discs are added to the array, theprobability of a disc failure increases, which increases the demand formaintenance. For example, when a disc fails, it needs to be manuallyreplaced before another disc fails and the data stored in the RAIDdevice is lost. To reduce the risk of data loss, data on a RAID deviceis typically copied on to one or more other RAID devices. While thisaddresses the loss of data issue, it raises a security issue sincemultiple copies of data are available, which increases the chances ofunauthorized access. Further, as the amount of data being stored grows,the overhead of RAID devices becomes a non-trivial efficiency issue.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a computingsystem in accordance with the invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the invention;

FIG. 3 is a schematic block diagram of an embodiment of a distributedstorage processing unit in accordance with the invention;

FIG. 4 is a schematic block diagram of an embodiment of a grid module inaccordance with the invention;

FIG. 5 is a diagram of an example embodiment of error coded data slicecreation in accordance with the invention;

FIG. 6A is a schematic block diagram of another embodiment of acomputing system in accordance with the invention;

FIG. 6B is a diagram illustrating an example of data and parityassignments to memory in accordance with the invention;

FIG. 6C is a diagram illustrating an example of converting data storagebetween RAID formatting and DSN formatting in accordance with theinvention;

FIG. 7 is a flowchart illustrating an example of storing data inaccordance with the invention;

FIG. 8 is a flowchart illustrating an example of retrieving data inaccordance with the invention;

FIG. 9A is a schematic block diagram of another embodiment of acomputing system in accordance with the invention;

FIG. 9B is a flowchart illustrating an example of copying data inaccordance with the invention;

FIG. 10 is a flowchart illustrating another example of copying data inaccordance with the invention;

FIG. 11 is a schematic block diagram of another embodiment of acomputing system in accordance with the invention;

FIG. 12 is a flowchart illustrating another example of storing data inaccordance with the invention;

FIG. 13 is a flowchart illustrating another example of copying data inaccordance with the invention;

FIG. 14 is a schematic block diagram of another embodiment of acomputing system in accordance with the invention;

FIG. 15 is a flowchart illustrating another example of storing data inaccordance with the invention;

FIG. 16 is a flowchart illustrating another example of retrieving datain accordance with the invention;

FIG. 17 is a flowchart illustrating an example of rebuilding data inaccordance with the invention;

FIG. 18 is a flowchart illustrating another example of storing data inaccordance with the invention;

FIG. 19 is a flowchart illustrating another example of retrieving datain accordance with the invention;

FIG. 20A is a flowchart illustrating another example of storing data inaccordance with the invention;

FIG. 20B is a flowchart illustrating an example of migrating data inaccordance with the invention;

FIG. 21 is a flowchart illustrating another example of retrieving datain accordance with the invention.

FIG. 22 is a schematic block diagram of another embodiment of acomputing system in accordance with the invention;

FIG. 23 is a flowchart illustrating another example of storing data inaccordance with the invention;

FIG. 24 is a schematic block diagram of another embodiment of acomputing system in accordance with the invention; and

FIG. 25 is a flowchart illustrating another example of storing data inaccordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of a computing system 10 thatincludes one or more of a first type of user devices 12, one or more ofa second type of user devices 14, at least one distributed storage (DS)processing unit 16, at least one DS managing unit 18, at least onestorage integrity processing unit 20, and a distributed storage network(DSN) memory 22 coupled via a network 24. The network 24 may include oneor more wireless and/or wire lined communication systems; one or moreprivate intranet systems and/or public internet systems; and/or one ormore local area networks (LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of distributed storage (DS) units36 for storing data of the system. Each of the DS units 36 includes aprocessing module and memory and may be located at a geographicallydifferent site than the other DS units (e.g., one in Chicago, one inMilwaukee, etc.). The processing module may be a single processingdevice or a plurality of processing devices. Such a processing devicemay be a microprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module may have an associatedmemory and/or memory element, which may be a single memory device, aplurality of memory devices, and/or embedded circuitry of the processingmodule. Such a memory device may be a read-only memory, random accessmemory, volatile memory, non-volatile memory, static memory, dynamicmemory, flash memory, cache memory, and/or any device that storesdigital information. Note that if the processing module includes morethan one processing device, the processing devices may be centrallylocated (e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that when the processing module implements one or more ofits functions via a state machine, analog circuitry, digital circuitry,and/or logic circuitry, the memory and/or memory element storing thecorresponding operational instructions may be embedded within, orexternal to, the circuitry comprising the state machine, analogcircuitry, digital circuitry, and/or logic circuitry. Still further notethat, the memory element stores, and the processing module executes,hard coded and/or operational instructions corresponding to at leastsome of the steps and/or functions illustrated in FIGS. 1-25.

Each of the user devices 12-14, the DS processing unit 16, the DSmanaging unit 18, and the storage integrity processing unit 20 may be aportable computing device (e.g., a social networking device, a gamingdevice, a cell phone, a smart phone, a personal digital assistant, adigital music player, a digital video player, a laptop computer, ahandheld computer, a video game controller, and/or any other portabledevice that includes a computing core) and/or a fixed computing device(e.g., a personal computer, a computer server, a cable set-top box, asatellite receiver, a television set, a printer, a fax machine, homeentertainment equipment, a video game console, and/or any type of homeor office computing equipment). Such a portable or fixed computingdevice includes a computing core 26 and one or more interfaces 30, 32,and/or 33. An embodiment of the computing core 26 will be described withreference to FIG. 2.

With respect to the interfaces, each of the interfaces 30, 32, and 33includes software and/or hardware to support one or more communicationlinks via the network 24 and/or directly. For example, interfaces 30support a communication link (wired, wireless, direct, via a LAN, viathe network 24, etc.) between the first type of user device 14 and theDS processing unit 16. As another example, DSN interface 32 supports aplurality of communication links via the network 24 between the DSNmemory 22 and the DS processing unit 16, the first type of user device12, and/or the storage integrity processing unit 20. As yet anotherexample, interface 33 supports a communication link between the DSmanaging unit 18 and any one of the other devices and/or units 12, 14,16, 20, and/or 22 via the network 24.

In general and with respect to data storage, the computing system 10supports three primary functions: distributed network data storagemanagement, distributed data storage and retrieval, and data storageintegrity verification. In accordance with these three primaryfunctions, data can be distributedly stored in a plurality of physicallydifferent locations and subsequently retrieved in a reliable and securemanner regardless of failures of individual storage devices, failures ofnetwork equipment, the duration of storage, the amount of data beingstored, attempts at hacking the data, etc.

The DS managing unit 18 performs distributed network data storagemanagement functions, which include establishing distributed datastorage parameters, performing network operations, performing networkadministration, and/or performing network maintenance. The DS managingunit 18 establishes the distributed data storage parameters (e.g.,allocation of virtual DSN memory space, distributed storage parameters,security parameters, billing information, user profile information,etc.) for one or more of the user devices 12-14 (e.g., established forindividual devices, established for a user group of devices, establishedfor public access by the user devices, etc.). For example, the DSmanaging unit 18 coordinates the creation of a vault (e.g., a virtualmemory block) within the DSN memory 22 for a user device (for a group ofdevices, or for public access). The DS managing unit 18 also determinesthe distributed data storage parameters for the vault. In particular,the DS managing unit 18 determines a number of slices (e.g., the numberthat a data segment of a data file and/or data block is partitioned intofor distributed storage) and a read threshold value (e.g., the minimumnumber of slices required to reconstruct the data segment).

As another example, the DS managing module 18 creates and stores,locally or within the DSN memory 22, user profile information. The userprofile information includes one or more of authentication information,permissions, and/or the security parameters. The security parameters mayinclude one or more of encryption/decryption scheme, one or moreencryption keys, key generation scheme, and data encoding/decodingscheme.

As yet another example, the DS managing unit 18 creates billinginformation for a particular user, user group, vault access, publicvault access, etc. For instance, the DS managing unit 18 tracks thenumber of times user accesses a private vault and/or public vaults,which can be used to generate a per-access bill. In another instance,the DS managing unit 18 tracks the amount of data stored and/orretrieved by a user device and/or a user group, which can be used togenerate a per-data-amount bill.

The DS managing unit 18 also performs network operations, networkadministration, and/or network maintenance. As at least part ofperforming the network operations and/or administration, the DS managingunit 18 monitors performance of the devices and/or units of thecomputing system 10 for potential failures, determines the devicesand/or unit's activation status, determines the devices' and/or units'loading, and any other system level operation that affects theperformance level of the computing system 10. For example, the DSmanaging unit 18 receives and aggregates network management alarms,alerts, errors, status information, performance information, andmessages from the devices 12-14 and/or the units 16, 20, 22. Forexample, the DS managing unit 18 receives a simple network managementprotocol (SNMP) message regarding the status of the DS processing unit16.

The DS managing unit 18 performs the network maintenance by identifyingequipment within the computing system 10 that needs replacing,upgrading, repairing, and/or expanding. For example, the DS managingunit 18 determines that the DSN memory 22 needs more DS units 36 or thatone or more of the DS units 36 needs updating.

The second primary function (i.e., distributed data storage andretrieval) begins and ends with a user device 12-14. For instance, if asecond type of user device 14 has a data file 38 and/or data block 40 tostore in the DSN memory 22, it send the data file 38 and/or data block40 to the DS processing unit 16 via its interface 30. As will bedescribed in greater detail with reference to FIG. 2, the interface 30functions to mimic a conventional operating system (OS) file systeminterface (e.g., network file system (NFS), flash file system (FFS),disk file system (DFS), file transfer protocol (FTP), web-baseddistributed authoring and versioning (WebDAV), etc.) and/or a blockmemory interface (e.g., small computer system interface (SCSI), internetsmall computer system interface (iSCSI), etc.). In addition, theinterface 30 may attach a user identification code (ID) to the data file38 and/or data block 40.

The DS processing unit 16 receives the data file 38 and/or data block 40via its interface 30 and performs a distributed storage (DS) process 34thereon (e.g., an error coding dispersal storage function). The DSprocessing 34 begins by partitioning the data file 38 and/or data block40 into one or more data segments, which is represented as Y datasegments. For example, the DS processing 34 may partition the data file38 and/or data block 40 into a fixed byte size segment (e.g., 2¹ to2^(n) bytes, where n=>2) or a variable byte size (e.g., change byte sizefrom segment to segment, or from groups of segments to groups ofsegments, etc.).

For each of the Y data segments, the DS processing 34 error encodes(e.g., forward error correction (FEC), information dispersal algorithm,or error correction coding) and slices (or slices then error encodes)the data segment into a plurality of error coded (EC) data slices 42-48,which is represented as X slices per data segment. The number of slices(X) per segment, which corresponds to a number of pillars n, is set inaccordance with the distributed data storage parameters and the errorcoding scheme. For example, if a Reed-Solomon (or other FEC scheme) isused in an n/k system, then a data segment is divided into n slices,where k number of slices is needed to reconstruct the original data(i.e., k is the threshold). As a few specific examples, the n/k factormay be 5/3; 6/4; 8/6; 8/5; 16/10.

For each EC slice 42-48, the DS processing unit 16 creates a uniqueslice name and appends it to the corresponding EC slice 42-48. The slicename includes universal DSN memory addressing routing information (e.g.,virtual memory addresses in the DSN memory 22) and user-specificinformation (e.g., user ID, file name, data block identifier, etc.).

The DS processing unit 16 transmits the plurality of EC slices 42-48 toa plurality of DS units 36 of the DSN memory 22 via the DSN interface 32and the network 24. The DSN interface 32 formats each of the slices fortransmission via the network 24. For example, the DSN interface 32 mayutilize an internet protocol (e.g., TCP/IP, etc.) to packetize the ECslices 42-48 for transmission via the network 24.

The number of DS units 36 receiving the EC slices 42-48 is dependent onthe distributed data storage parameters established by the DS managingunit 18. For example, the DS managing unit 18 may indicate that eachslice is to be stored in a different DS unit 36. As another example, theDS managing unit 18 may indicate that like slice numbers of differentdata segments are to be stored in the same DS unit 36. For example, thefirst slice of each of the data segments is to be stored in a first DSunit 36, the second slice of each of the data segments is to be storedin a second DS unit 36, etc. In this manner, the data is encoded anddistributedly stored at physically diverse locations to improved datastorage integrity and security. Further examples of encoding the datasegments will be provided with reference to one or more of FIGS. 2-25.

Each DS unit 36 that receives an EC slice 42-48 for storage translatesthe virtual DSN memory address of the slice into a local physicaladdress for storage. Accordingly, each DS unit 36 maintains a virtual tophysical memory mapping to assist in the storage and retrieval of data.

The first type of user device 12 performs a similar function to storedata in the DSN memory 22 with the exception that it includes the DSprocessing. As such, the device 12 encodes and slices the data fileand/or data block it has to store. The device then transmits the slices11 to the DSN memory via its DSN interface 32 and the network 24.

For a second type of user device 14 to retrieve a data file or datablock from memory, it issues a read command via its interface 30 to theDS processing unit 16. The DS processing unit 16 performs the DSprocessing 34 to identify the DS units 36 storing the slices of the datafile and/or data block based on the read command. The DS processing unit16 may also communicate with the DS managing unit 18 to verify that theuser device 14 is authorized to access the requested data.

Assuming that the user device is authorized to access the requesteddata, the DS processing unit 16 issues slice read commands to at least athreshold number of the DS units 36 storing the requested data (e.g., toat least 10 DS units for a 16/10 error coding scheme). Each of the DSunits 36 receiving the slice read command, verifies the command,accesses its virtual to physical memory mapping, retrieves the requestedslice, or slices, and transmits it to the DS processing unit 16.

Once the DS processing unit 16 has received a read threshold number ofslices for a data segment, it performs an error decoding function andde-slicing to reconstruct the data segment. When Y number of datasegments has been reconstructed, the DS processing unit 16 provides thedata file 38 and/or data block 40 to the user device 14. Note that thefirst type of user device 12 performs a similar process to retrieve adata file and/or data block.

The storage integrity processing unit 20 performs the third primaryfunction of data storage integrity verification. In general, the storageintegrity processing unit 20 periodically retrieves slices 45, and/orslice names, of a data file or data block of a user device to verifythat one or more slices have not been corrupted or lost (e.g., the DSunit failed). The retrieval process mimics the read process previouslydescribed.

If the storage integrity processing unit 20 determines that one or moreslices is corrupted or lost, it rebuilds the corrupted or lost slice(s)in accordance with the error coding scheme. The storage integrityprocessing unit 20 stores the rebuild slice, or slices, in theappropriate DS unit(s) 36 in a manner that mimics the write processpreviously described.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an interface 60, at least one IO device interface module 62, a read onlymemory (ROM) basic input output system (BIOS) 64, and one or more memoryinterface modules. The memory interface module(s) includes one or moreof a universal serial bus (USB) interface module 66, a host bus adapter(HBA) interface module 68, a network interface module 70, a flashinterface module 72, a hard drive interface module 74, and a DSNinterface module 76. Note the DSN interface module 76 and/or the networkinterface module 70 may function as the interface 30 of the user device14 of FIG. 1. Further note that the IO device interface module 62 and/orthe memory interface modules may be collectively or individuallyreferred to as IO ports.

The processing module 50 may be a single processing device or aplurality of processing devices. Such a processing device may be amicroprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module 50 may have anassociated memory and/or memory element, which may be a single memorydevice, a plurality of memory devices, and/or embedded circuitry of theprocessing module 50. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module 50includes more than one processing device, the processing devices may becentrally located (e.g., directly coupled together via a wired and/orwireless bus structure) or may be distributedly located (e.g., cloudcomputing via indirect coupling via a local area network and/or a widearea network). Further note that when the processing module 50implements one or more of its functions via a state machine, analogcircuitry, digital circuitry, and/or logic circuitry, the memory and/ormemory element storing the corresponding operational instructions may beembedded within, or external to, the circuitry comprising the statemachine, analog circuitry, digital circuitry, and/or logic circuitry.Still further note that, the memory element stores, and the processingmodule 50 executes, hard coded and/or operational instructionscorresponding to at least some of the steps and/or functions illustratedin FIGS. 1-25.

FIG. 3 is a schematic block diagram of an embodiment of a dispersedstorage (DS) processing module 34 of user device 12 and/or of the DSprocessing unit 16. The DS processing module 34 includes a gatewaymodule 78, an access module 80, a grid module 82, and a storage module84. The DS processing module 34 may also include an interface 30 and theDSnet interface 32 or the interfaces 68 and/or 70 may be part of user 12or of the DS processing unit 16. The DS processing module 34 may furtherinclude a bypass/feedback path between the storage module 84 to thegateway module 78. Note that the modules 78-84 of the DS processingmodule 34 may be in a single unit or distributed across multiple units.

In an example of storing data, the gateway module 78 receives anincoming data object that includes a user ID field 86, an object namefield 88, and the data field 40 and may also receive correspondinginformation that includes a process identifier (e.g., an internalprocess/application ID), metadata, a file system directory, a blocknumber, a transaction message, a user device identity (ID), a dataobject identifier, a source name, and/or user information. The gatewaymodule 78 authenticates the user associated with the data object byverifying the user ID 86 with the DS managing unit 18 and/or anotherauthenticating unit.

When the user is authenticated, the gateway module 78 obtains userinformation from the DS management unit 18, the user device, and/or theother authenticating unit. The user information includes a vaultidentifier, operational parameters, and user attributes (e.g., userdata, billing information, etc.). A vault identifier identifies a vault,which is a virtual memory space that maps to a set of DS storage units36. For example, vault 1 (i.e., user 1's DSN memory space) includeseight DS storage units (X=8 wide) and vault 2 (i.e., user 2's DSN memoryspace) includes sixteen DS storage units (X=16 wide). The operationalparameters may include an error coding algorithm, the width n (number ofpillars X or slices per segment for this vault), a read threshold T, awrite threshold, an encryption algorithm, a slicing parameter, acompression algorithm, an integrity check method, caching settings,parallelism settings, and/or other parameters that may be used to accessthe DSN memory layer.

The gateway module 78 uses the user information to assign a source name35 to the data. For instance, the gateway module 78 determines thesource name 35 of the data object 40 based on the vault identifier andthe data object. For example, the source name may contain a fileidentifier (ID), a vault generation number, a reserved field, and avault identifier (ID). As another example, the gateway module 78 maygenerate the file ID based on a hash function of the data object 40.Note that the gateway module 78 may also perform message conversion,protocol conversion, electrical conversion, optical conversion, accesscontrol, user identification, user information retrieval, trafficmonitoring, statistics generation, configuration, management, and/orsource name determination.

The access module 80 receives the data object 40 and creates a series ofdata segments 1 through Y 90-92 in accordance with a data storageprotocol (e.g., file storage system, a block storage system, and/or anaggregated block storage system). The number of segments Y may be chosenor randomly assigned based on a selected segment size and the size ofthe data object. For example, if the number of segments is chosen to bea fixed number, then the size of the segments varies as a function ofthe size of the data object. For instance, if the data object is animage file of 4,194,304 eight bit bytes (e.g., 33,554,432 bits) and thenumber of segments Y=131,072, then each segment is 256 bits or 32 bytes.As another example, if segment sized is fixed, then the number ofsegments Y varies based on the size of data object. For instance, if thedata object is an image file of 4,194,304 bytes and the fixed size ofeach segment is 4,096 bytes, the then number of segments Y=1,024. Notethat each segment is associated with the same source name.

The grid module 82 receives the data segments and may manipulate (e.g.,compression, encryption, cyclic redundancy check (CRC), etc.) each ofthe data segments before performing an error coding function of theerror coding dispersal storage function to produce a pre-manipulateddata segment. After manipulating a data segment, if applicable, the gridmodule 82 error encodes (e.g., Reed-Solomon, Convolution encoding,Trellis encoding, etc.) the data segment or manipulated data segmentinto X error coded data slices 42-48.

The value X, or the number of pillars (e.g., X=16), is chosen as aparameter of the error coding dispersal storage function. Otherparameters of the error coding dispersal function include a readthreshold T, a write threshold W, etc. The read threshold (e.g., T=10,when X=16) corresponds to the minimum number of error-free error codeddata slices required to reconstruct the data segment. In other words,the DS processing module 34 can compensate for X-T (e.g., 16−10=6)missing error coded data slices per data segment. The write threshold Wcorresponds to a minimum number of DS storage units that acknowledgeproper storage of their respective data slices before the DS processingmodule indicates proper storage of the encoded data segment. Note thatthe write threshold is greater than or equal to the read threshold for agiven number of pillars (X).

For each data slice of a data segment, the grid module 82 generates aunique slice name 37 and attaches it thereto. The slice name 37 includesa universal routing information field and a vault specific field and maybe 48 bytes (e.g., 24 bytes for each of the universal routinginformation field and the vault specific field). As illustrated, theuniversal routing information field includes a slice index, a vault ID,a vault generation, and a reserved field. The slice index is based onthe pillar number and the vault ID and, as such, is unique for eachpillar (e.g., slices of the same pillar for the same vault for anysegment will share the same slice index). The vault specific fieldincludes a data name, which includes a file ID and a segment number(e.g., a sequential numbering of data segments 1-Y of a simple dataobject or a data block number).

Prior to outputting the error coded data slices of a data segment, thegrid module may perform post-slice manipulation on the slices. Ifenabled, the manipulation includes slice level compression, encryption,CRC, addressing, tagging, and/or other manipulation to improve theeffectiveness of the computing system.

When the error coded data slices of a data segment are ready to beoutputted, the grid module 82 determines which of the DS storage units36 will store the EC data slices based on a dispersed storage memorymapping associated with the user's vault and/or DS storage unitattributes. The DS storage unit attributes may include availability,self-selection, performance history, link speed, link latency,ownership, available DSN memory, domain, cost, a prioritization scheme,a centralized selection message from another source, a lookup table,data ownership, and/or any other factor to optimize the operation of thecomputing system. Note that the number of DS storage units 36 is equalto or greater than the number of pillars (e.g., X) so that no more thanone error coded data slice of the same data segment is stored on thesame DS storage unit 36. Further note that EC data slices of the samepillar number but of different segments (e.g., EC data slice 1 of datasegment 1 and EC data slice 1 of data segment 2) may be stored on thesame or different DS storage units 36.

The storage module 84 performs an integrity check on the outboundencoded data slices and, when successful, identifies a plurality of DSstorage units based on information provided by the grid module 82. Thestorage module 84 then outputs the encoded data slices 1 through X ofeach segment 1 through Y to the DS storage units 36. Each of the DSstorage units 36 stores its EC data slice(s) and maintains a localvirtual DSN address to physical location table to convert the virtualDSN address of the EC data slice(s) into physical storage addresses.

In an example of a read operation, the user device 12 and/or 14 sends aread request to the DS processing unit 16, which authenticates therequest. When the request is authentic, the DS processing unit 16 sendsa read message to each of the DS storage units 36 storing slices of thedata object being read. The slices are received via the DSnet interface32 and processed by the storage module 84, which performs a parity checkand provides the slices to the grid module 82 when the parity check wassuccessful. The grid module 82 decodes the slices in accordance with theerror coding dispersal storage function to reconstruct the data segment.The access module 80 reconstructs the data object from the data segmentsand the gateway module 78 formats the data object for transmission tothe user device.

FIG. 4 is a schematic block diagram of an embodiment of a grid module 82that includes a control unit 73, a pre-slice manipulator 75, an encoder77, a slicer 79, a post-slice manipulator 81, a pre-slice de-manipulator83, a decoder 85, a de-slicer 87, and/or a post-slice de-manipulator 89.Note that the control unit 73 may be partially or completely external tothe grid module 82. For example, the control unit 73 may be part of thecomputing core at a remote location, part of a user device, part of theDS managing unit 18, or distributed amongst one or more DS storageunits.

In an example of write operation, the pre-slice manipulator 75 receivesa data segment 90-92 and a write instruction from an authorized userdevice. The pre-slice manipulator 75 determines if pre-manipulation ofthe data segment 90-92 is required and, if so, what type. The pre-slicemanipulator 75 may make the determination independently or based oninstructions from the control unit 73, where the determination is basedon a computing system-wide predetermination, a table lookup, vaultparameters associated with the user identification, the type of data,security requirements, available DSN memory, performance requirements,and/or other metadata.

Once a positive determination is made, the pre-slice manipulator 75manipulates the data segment 90-92 in accordance with the type ofmanipulation. For example, the type of manipulation may be compression(e.g., Lempel-Ziv-Welch, Huffman, Golomb, fractal, wavelet, etc.),signatures (e.g., Digital Signature Algorithm (DSA), Elliptic Curve DSA,Secure Hash Algorithm, etc.), watermarking, tagging, encryption (e.g.,Data Encryption Standard, Advanced Encryption Standard, etc.), addingmetadata (e.g., time/date stamping, user information, file type, etc.),cyclic redundancy check (e.g., CRC32), and/or other data manipulationsto produce the pre-manipulated data segment.

The encoder 77 encodes the pre-manipulated data segment 90-92 using aforward error correction (FEC) encoder (and/or other type of erasurecoding and/or error coding) to produce an encoded data segment 94. Theencoder 77 determines which forward error correction algorithm to usebased on a predetermination associated with the user's vault, a timebased algorithm, user direction, DS managing unit direction, controlunit direction, as a function of the data type, as a function of thedata segment 90-92 metadata, and/or any other factor to determinealgorithm type. The forward error correction algorithm may be Golay,Multidimensional parity, Reed-Solomon, Hamming, Bose Ray ChauduriHocquenghem (BCH), Cauchy-Reed-Solomon, or any other FEC encoder. Notethat the encoder 77 may use a different encoding algorithm for each datasegment 90-92, the same encoding algorithm for the data segments 90-92of a data object, or a combination thereof.

The encoded data segment 94 is of greater size than the data segment90-92 by the overhead rate of the encoding algorithm by a factor of X/T,where X is the width or number of slices, and T is the read threshold.In this regard, the corresponding decoding process can accommodate atmost X-T missing EC data slices and still recreate the data segment90-92. For example, if X=16 and T=10, then the data segment 90-92 willbe recoverable as long as 10 or more EC data slices per segment are notcorrupted.

The slicer 79 transforms the encoded data segment 94 into EC data slicesin accordance with the slicing parameter from the vault for this userand/or data segment 90-92. For example, if the slicing parameter isX=16, then the slicer 79 slices each encoded data segment 94 into 16encoded slices.

The post-slice manipulator 81 performs, if enabled, post-manipulation onthe encoded slices to produce the EC data slices. If enabled, thepost-slice manipulator 81 determines the type of post-manipulation,which may be based on a computing system-wide predetermination,parameters in the vault for this user, a table lookup, the useridentification, the type of data, security requirements, available DSNmemory, performance requirements, control unit directed, and/or othermetadata. Note that the type of post-slice manipulation may includeslice level compression, signatures, encryption, CRC, addressing,watermarking, tagging, adding metadata, and/or other manipulation toimprove the effectiveness of the computing system.

In an example of a read operation, the post-slice de-manipulator 89receives at least a read threshold number of EC data slices and performsthe inverse function of the post-slice manipulator 81 to produce aplurality of encoded slices. The de-slicer 87 de-slices the encodedslices to produce an encoded data segment 94. The decoder 85 performsthe inverse function of the encoder 77 to recapture the data segment90-92. The pre-slice de-manipulator 83 performs the inverse function ofthe pre-slice manipulator 75 to recapture the data segment 90-92.

FIG. 5 is a diagram of an example of slicing an encoded data segment 94by the slicer 79. In this example, the encoded data segment 94 includesthirty-two bits, but may include more or less bits. The slicer 79disperses the bits of the encoded data segment 94 across the EC dataslices in a pattern as shown. As such, each EC data slice does notinclude consecutive bits of the data segment 94 reducing the impact ofconsecutive bit failures on data recovery. For example, if EC data slice2 (which includes bits 1, 5, 9, 13, 17, 25, and 29) is unavailable(e.g., lost, inaccessible, or corrupted), the data segment can bereconstructed from the other EC data slices (e.g., 1, 3 and 4 for a readthreshold of 3 and a width of 4).

FIG. 6A is a schematic block diagram of another embodiment of acomputing system that includes one or more of a first type of userdevices 12, one or more of a second type of user devices 14, a dispersedstorage (DS) processing unit 16, and a dispersed storage network (DSN)memory 22. Note that the DSN memory 22 includes a plurality of DS units36, wherein the DS units 36 may be deployed at one or more sites. Userdevice 14 includes a computing core 26, wherein the computing core 26includes a redundant array of independent disks (RAID) controller 106.User device 12 includes the computing core 26, wherein the computingcore 26 includes the RAID controller 106 and a DS processing 34.

The RAID controller 106 receives data (e.g., data in the format of datablocks, data objects, and/or data files in accordance with a filesystem) from the computing core 26 and creates RAID data from the datain accordance with a RAID method. Such a RAID method is discussed ingreater detail with reference to FIG. 6B. The data provided by thecomputing core 26 to the RAID controller 106 may be referenced by one ormore of a data object name, a file name, a block number, a data objectidentifier (ID), and/or a file ID. In addition, the data is described bymetadata, which may include one or more of a data type, a data size, apriority indicator, a security indicator, a performance indicator, auser ID, a group ID, a timestamp, and other descriptors to describe thedata.

The RAID controller 106 produces RAID data that includes the data andone or more of metadata commands, memory information, statusinformation, and requests. Such commands include one or more of write,read, delete, status, erase, and invert. Such memory informationincludes physical addresses utilized within a RAID memory. For example,the RAID controller 106 of user device 14 sends RAID data 110 to the DSprocessing unit 16 such that the DS processing unit 16 facilitatesstoring data of the RAID data 110 in the DSN memory 22 as encoded dataslices 11. As another example, the RAID controller 106 of user device 12sends RAID data to the DS processing 34 such that the DS processing 34facilitates storing data of the RAID data in the DSN memory 22 as theencoded data slices 11.

In an example of a data storage operation, the DS processing unit 16receives RAID data 110 from the RAID controller 106 of user device 14,wherein the RAID data includes a store command and the data. The DSprocessing unit 16 determines a DS storage method, wherein the DSstorage method includes creating encoded data slices of the data basedon the entire data object (e.g., all the RAID blocks in aggregate) orcreating encoded data slices based on one RAID block at a time. Next,the DS processing unit 16 creates encoded data slices based on the RAIDdata in accordance with the DS storage method. The DS processing unit 16sends the encoded data slices 11 to the DSN memory 22 for storagetherein. Note that the DS processing 34 of user device 12 operates in asimilar manner to store data of RAID data from the RAID controller 106of the user device 12 as encoded data slices 11 in the DSN memory 22.The method to create the encoded data slices 11 based on the RAID datais discussed in greater detail with reference to FIG. 7.

In an example of a data retrieval operation, the DS processing unit 16receives RAID data 110 from the RAID controller 106, wherein the RAIDdata includes a retrieve command. The DS processing unit 16 determines aDSN memory location of encoded data slices corresponding to requestedRAID data. The DS processing unit 16 retrieves encoded data slices 11from the DSN memory 22 at the DSN memory location and determines the DSstorage method. The DS processing unit 16 recovers the requested RAIDdata from the retrieved encoded data slices in accordance with the DSstorage method and the RAID format. The DS processing unit 16 sends therequested RAID data to the RAID controller 106. The method to recoverRAID data is discussed in greater detail with reference to FIG. 8.

FIG. 6B is a diagram illustrating an example of data and parityassignments to memory that includes data stripes A-B assigned tomemories 1-3. Such memories 1-3 are included in a redundant array ofindependent disks (RAID) memory and are assigned to store RAID data as aplurality of data stripes that each includes a plurality of blocks. Suchblocks includes RAID block data or RAID parity data created inaccordance with a RAID method based on data to be stored. Such a RAIDmethod includes an approach to produce and store RAID data based on thedata to be stored and in accordance with one or more industry RAIDstandards and/or techniques (e.g., RAID 0-6). One such approach toproduce and store RAID data includes dividing the data into RAID blockdata blocks and storing the RAID block data blocks in differentmemories.

Another approach to produce and store RAID data includes dividing thedata into RAID block data blocks, replicating at least some of the RAIDblock data blocks to produce replicated RAID block data blocks, andstoring the RAID block data blocks and the replicated RAID block datablocks in different memories. Still another approach to produce andstore RAID data includes dividing the data into RAID block data blocks,calculating RAID parity blocks, and storing the RAID block data blocksand the RAID parity data blocks in different memories. For example, datais converted into RAID data in accordance with the RAID method; whereinthe RAID data includes a plurality of data stripes A, B, etc. Each datastripe of the plurality of data stripes includes a set of three blocks,wherein the set of three blocks includes two RAID block data blocks andone RAID parity data block. In a specific example, a logical exclusiveOR (XOR) is calculated of a first RAID block data block of the two RAIDlike data blocks with a second RAID block data block to produce the RAIDparity data block. Note that the data stripe is reproducible when anytwo blocks of the set of three blocks is available. Each block of theset of three blocks is assigned to one memory of the RAID memory forstorage therein. For example, stripe A RAID block data block 1 isassigned to memory 1, stripe A RAID block data block 2 is assigned tomemory 2, and stripe A RAID parity data block is assigned to memory 3.

FIG. 6C is a diagram illustrating an example of converting data storagebetween RAID formatting and DSN formatting. In this example, RAID data110 includes data, metadata, and a RAID operation (e.g., one or more ofmetadata commands, memory information, status information, andrequests). The RAID data 110 may be stored using RAID formatting and/orDSN formatting. For RAID formatting, the data (which may include themetadata) is arranged into stripes (e.g., rows A, B, through x) and eachstripe includes a plurality of columns (3 in this example, but mayinclude more). Two of the stripe blocks each includes a data block andthe third includes a parity data, which is produced by exclusive ORingthe other two data blocks.

The DSN formatting segments the data (which may further include themetadata) into one or more data segments (n number of data segments areshown in this example). Each of the data segments is error encoded usingan error coding dispersal storage function to produce a set of encodeddata slices (e.g., 1 through p, where p represents the pillar width ofthe error coding dispersal storage function).

The DS processing unit 16 functions to allow the RAID data 110 to bestored in accordance with the RAID formatting, the DSN formatting,and/or converted therebetween. For example, the DS processing unit 16enables the RAID data to be stored in accordance with the RAID format inRAID memory (not shown in this figure). As such, the DS processing unit16 would pass the RAID data to the RAID memory for storage therein.Alternatively, the DS processing unit 16 performs the RAID formatting onthe RAID data 110 and stores the RAID formatted data in local memory,RAID memory, a section of the DSN memory 22 reserved for RAID storage,and/or some other memory.

In another example, the DS processing unit 16 enables the RAID data 110to be stored in the DSN formatting in the DSN memory 22. In thisinstance, the DS processing unit 16 segments the data and error encodesthe segments as previously discussed.

In yet another example, the DS processing unit 16 (or other processingmodule) determines to convert stored data from the RAID format to theDSN format. In this instance, the DS processing unit 16 retrieves asufficient number of data blocks per stripe to produce the original data(e.g., blocks 1 and 2 and not the parity data block). The DS processingunit 16 reconstructs the data from the retrieved data blocks, segmentsthe reconstructed data and error encodes the segments to produce aplurality of sets of encoded data slices.

In a further example, the DS processing unit 16 (or other processingmodule) determines to convert stored data from the DSN format to theRAID format. In this instance, the DS processing unit 16 reconstructsthe data from the plurality of sets of encoded data slices. The DSprocessing unit 16 then partitions the reconstructed data into stripes,which includes two or more data blocks. The DS processing unit 16 thencreates parity data for each stripe from the data blocks. The resultingRAID formatted data may be stored in RAID memory, local memory, asection of the DSN memory 22 reserved for RAID storage, and/or someother memory.

FIG. 7 is a flowchart illustrating an example of storing data. A methodbegins with step 114 where a processing module receives data for storageand interprets the data to identify the data as redundant array ofindependent disks (RAID) data. For example, the processing modulereceives a RAID data storage request message from a RAID controller.Such a RAID data storage request message may include one or more of theRAID data, a RAID data storage request, a data object name, a dataobject, a data object size, a data type, a data block, parityinformation, a user identifier (ID), RAID unit information, disk driveinformation, address information, memory information, a command, andRAID method information. As another example, the processing module sendsa request to a RAID memory device regarding the RAID data and receivesthe RAID data from the RAID memory device.

The method continues at step 116 where the processing module determinesa dispersed storage (DS) method where the DS method includes producingencoded data slices based on one RAID block at a time and/or producingencoded data slices based on all the data at once. This step may furtherinclude identifying one or more of a first pillar slice portion and asecond pillar slice portion (e.g., which portion to send to which memorywhen multiple memories are available). Such a determination is based onone or more of interpreting the RAID data to identify at least one ofRAID block data and RAID parity data, a vault lookup, RAID memoryconfiguration information, a dispersed storage network memoryconfiguration, memory capability information, a comparison of memorycapability information of memories, a command, a message, apredetermination, a data object name, a data object, a data object size,a data type, a data block, parity information, a user identifier (ID),RAID unit information, disk drive information, address information,memory information, a command, and a request. For example, theprocessing module determines the DS method to include encoding the RAIDblock data in accordance with error coded dispersal storage optionparameters to produce at least one set of encoded data slices when theRAID data includes RAID block data and RAID parity data. As anotherexample, the processing module determines the DS method to includeproducing encoded data slices based on one RAID block at a time when avault lookup for this user ID indicates to produce encoded data slicesbased on one RAID block at a time.

The method continues at step 118 where the processing module determineserror coding dispersal storage function parameters (e.g., operationalparameters) where the error coding dispersal storage function parametersmay include one or more of a RAID method, a pillar width, a readthreshold, a decode threshold, a write threshold, an encode algorithm, adecode algorithm, an encryption method, an encryption key, a source namebased on the data object name, and dispersed storage network (DSN)storage location information. Such a determination may be based on atleast one of the RAID data, detection of the RAID block data, the RAIDparity data, detection of a RAID data stripe, RAID data checksuminformation, a vault lookup, RAID memory configuration information, acommand, a message, a predetermination, a data object name, a dataobject, a data object size, a data type, a data block, parityinformation, a user identifier (ID), RAID unit information, disk driveinformation, address information, memory information, a command, and arequest.

The method continues at step 120 where the processing module encodes theRAID block data based on the DS method and in accordance with the errorcoding dispersal storage function parameters to produce at least one setof encoded data slices when the RAID data includes RAID block data andRAID parity data. For example, the processing module determines anaccuracy of the RAID block data based on the RAID parity data (e.g.,utilize the RAID parity data to re-create RAID block data, compare therecreated RAID block data with the RAID block data to determine theaccuracy of the RAID block data) and when the accuracy of the RAID blockdata compares unfavorably to a desired accuracy (e.g., not the same dueto errors), correcting the RAID block data based on the RAID paritydata, and encodes the RAID block data to produce the at least one set ofencoded data slices. The method continues at step 122 where theprocessing module outputs the at least one set of encoded data slices toa dispersed storage network (DSN) memory for storage therein.

Alternatively, when the RAID data only includes the RAID parity data,the processing module encodes the RAID parity data in accordance withthe error coding dispersal storage function parameters to produce the atleast one set of encoded parity slices and outputs the at least one setof encoded parity slices to the DSN memory for storage therein.

FIG. 8 is a flowchart illustrating an example of retrieving data, whichincludes similar steps to FIG. 7. A method begins with step 124 where aprocessing module receives a data retrieval request from a requester andinterprets the data retrieval request to identify the data retrievalrequest as a redundant array of independent disks (RAID) data retrievalrequest. For example, the processing module receives a RAID dataretrieval request message from a RAID controller. Such a RAID dataretrieval request message may include one or more of the data retrievalrequest, a data object name, a data object size, a data type, a useridentifier (ID), RAID unit information, disk drive information, addressinformation, memory information, a command, and RAID method information.The method continues at step 118 of FIG. 7 to determine error codingdispersal storage option parameters.

The method continues at step 126 where the processing module retrievesat least one set of encoded data slices from a dispersed storage network(DSN) memory based on the RAID data retrieval request. For example, theprocessing module determines a DSN address corresponding to the at leastone set of encoded data slices based on the data object name included inthe RAID data retrieval request, sends at least one encoded data sliceretrieval request to the DSN memory that includes the DSN addresscorresponding to the response of encoded data slices, and receives atleast a decode threshold number of encoded data slices of the at leastone set of encoded data slices from the DSN memory in response. Themethod continues at step 116 of FIG. 7 to determine a DS method.

The method continues at step 128 where the processing module dispersedstorage error decodes the at least one set of encoded data slices inaccordance with the error coding dispersal storage function parametersto produce RAID data. Next, the processing module interprets the RAIDdata to determine whether the RAID data represents a stripe of data or astripe-block of data (e.g., one block of RAID block data). Suchinterpreting of the RAID data includes interpreting a header section ofthe RAID data to determine whether the RAID data represents the stripeof data or the stripe-block of data. The processing module generatesRAID parity data from the RAID block of data of the RAID data when theRAID data represents the stripe of data. The method continues at step130 where the processing module outputs the RAID block data and the RAIDparity data to the requester. Alternatively, or in addition to, theprocessing module outputs the RAID data when the RAID data representsthe stripe-block of data.

FIG. 9A is a schematic block diagram of another embodiment of acomputing system that includes a user device 14, a dispersed storage(DS) processing unit 16, a redundant array of independent disks (RAID)memory 102, and a dispersed storage network (DSN) memory 22. Note thatthe DSN memory 22 includes a plurality of DS units 36, wherein the DSunits 36 may be deployed at one or more sites. User device 14 includes acomputing core 26, wherein the computing core 26 includes a RAIDcontroller 106. Alternatively, or in addition to, the user device 14 mayinclude a DS processing as discussed with reference to FIG. 6A.

The RAID memory 102 includes a plurality of RAID units 104. Such RAIDunits 104 include an associated memory and/or memory element, which maybe a single memory device or a plurality of memory devices. Such amemory device may be a read-only memory, a read-write memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, a magnetic disk drive,and/or any device that stores digital information. For example, the RAIDmemory 102 includes five RAID units 104, wherein each of the five RAIDunits 104 include at least one magnetic disk drive memory.

The RAID controller 106 stores RAID data 108 in the RAID memory 102and/or RAID data 110 in the DSN memory 22 via the DS processing unit 16.The DS processing unit 16 operates as previously discussed withreference to FIGS. 6A-8 to receive RAID data 110 and store the RAID data110 as encoded data slices 11 in the plurality of DS units 36 of the DSNmemory 22 and to retrieve the encoded data slices 11 from the DSN memory22 to reproduce the RAID data 110. In addition, the DS processing unit16 functions to backup RAID data 108 stored in the RAID memory 102 asdiscussed with reference to FIGS. 9A-10.

In an example of a data backup operation, the DS processing unit 16sends RAID data 112 (e.g., including a retrieve RAID data command) tothe RAID memory 102 to retrieve stored RAID data from the RAID memory102. Note that the DS processing unit 16 communicates with the RAIDmemory 102 utilizing RAID commands as utilized by the RAID controller106 to access the RAID memory 102. Next, the DS processing unit 16receives RAID data 112 from the RAID memory 102. The DS processing unit16 dispersed storage error encodes data of the RAID data 112 to produceencoded data slices. The DS processing unit 16 sends the encoded dataslices to the DSN memory 22 for storage therein. The method to copyand/or backup RAID data is discussed in greater detail with reference toFIGS. 9B and 10.

Alternatively, the user device 14 may be implemented as a user device 12that includes a DS processing 34 as discussed with reference to FIG. 6A.In an example of a data retrieval operation, the computing core 26determines to utilize the RAID controller 106 to retrieve data as RAIDdata 108 and/or RAID data 110 or to utilize the DS processing 34 todirectly retrieve encoded data slices from the DSN memory 22 toreproduce the data when the user device 12 includes the DS processing34. Such a determination may be based on one or more of estimated RAIDdata retrieval performance, estimated DSN data retrieval performance, aperformance goal, a query, performance history, a message, and acommand. For example, the computing core 26 determines to retrieve thedata as RAID data 108 from the RAID memory 102 when the estimated RAIDdata retrieval performance compares more favorably to the performancegoal than the estimated DSN data retrieval performance.

FIG. 9B is a flowchart illustrating an example of copying data, whichincludes many similar steps to FIG. 7. The method begins with step 132where a processing module determines redundant array of independentdisks (RAID) data to retrieve. Such RAID data may include data to copyand/or backup, wherein the RAID data is currently stored in a RAIDmemory. Such a determination may be based on one or more of whichportion of the RAID memory was most recently retrieved for copyingand/or backup, a particular RAID unit, a particular physical memory, aparticular RAID memory, an elapsed time since the last retrieval andstorage of the same RAID data, a command, a message, a predetermination,a vault lookup, and an error message.

The method continues at step 134 where the processing module retrievesthe RAID data. For example, the processing module retrieves the RAIDdata by sending a retrieve RAID data command to one or more of the RAIDunits of the RAID memory and receiving the RAID data in response. Such aretrieve RAID data command may include one or more of a command, RAIDunit information, disk drive information, address information, andmemory information. The method continues with steps 116, 118, 120, and122 of FIG. 7 to store the RAID data as encoded data slices in adispersed storage network (DSN) memory. Note that the processing modulemay indicate that the encoded data slices are associated with a newrevision of a data object that has been previously stored in the DSNmemory. The method repeats back to step 132 to copy more RAID data. Notethat the method provides a reliability improvement when a DS processingunit provides access to RAID data stored as encoded data slices in theDSN memory when the RAID memory fails.

FIG. 10 is a flowchart illustrating another example of copying data,which includes many similar steps to FIGS. 7, 8, and 9B. The methodbegins with steps 132 and 134 of FIG. 9B to retrieve current redundantarray of independent disks (RAID) data and then continues with steps 116and 118 of FIG. 7 and with steps 126 and 128 of FIG. 8 to re-createprior redundant array of independent disks (RAID) data from storedencoded data slices (e.g., stored in a dispersed storage network (DSN)memory), wherein the prior RAID data (e.g., a backup copy) is associatedwith the current RAID data (e.g., a working copy).

The method continues at step 136 where the processing module determinesif the prior RAID data compares favorably to the current RAID data basedon at least one comparison criteria. Such comparison criteria mayinclude one or more of comparing data of the prior RAID data to data ofthe current RAID data and/or comparing an age indicator of the priorRAID data to an age threshold. For example, the processing moduledetermines that the comparison is unfavorable when the prior RAID dataand the current RAID data are different. As another example, theprocessing module determines that the comparison is unfavorable when theage indicator of the prior RAID data is greater than the age threshold.

The method continues at step 138 where the processing module determinesRAID data metadata (e.g., of the current RAID data), wherein themetadata includes one or more of prior RAID data age, a backup frequencyindicator, an age threshold, a data type, a data size, a priorityindicator, a security indicator, a performance indicator, a user ID, agroup ID, a timestamp, and any other descriptors to describe the data.Such a determination may be based on one or more of the current RAIDdata, the prior RAID data, other RAID data, a vault lookup, a command, amessage, a predetermination, and an access frequency record.

The method continues at step 140 where the processing module determineswhether to store the current RAID data based on one or more of thecomparison of the prior RAID data to the current RAID data (e.g.,results of step 136), the RAID data metadata, a comparison of the priorRAID data age to the age threshold, a predetermination, a command, amessage, a vault lookup, and a comparison of access frequency to anaccess frequency threshold. For example, the processing moduledetermines to store (e.g., backup) the current RAID data when thecurrent RAID data is different than the prior RAID data and the priorRAID data age is above the age threshold. The method repeats back tostep 132 when the processing module determines to not store the currentRAID data. The method continues to step 120 of FIG. 7 when theprocessing module determines to store the current RAID data. The methodcontinues with steps 120 and 122 of FIG. 7 to store encoded data slicesof the RAID data (e.g., the current RAID data) in the DSN memory. Themethod branches back to step 132 to potentially retrieve and backup anext portion of the current RAID data.

FIG. 11 is a schematic block diagram of another embodiment of acomputing system that includes a user device 14, a dispersed storage(DS) processing unit 16, a redundant array of independent disks (RAID)memory 102, a local dispersed storage network (DSN) memory 22, and aremote DSN memory 23. The RAID memory 102 includes a plurality of RAIDunits 104. Note that the local DSN memory 22 and the remote DSN memory23 include a plurality of dispersed storage (DS) units 36, wherein theDS units 36 of the local DSN memory 22 are deployed at one or more siteswithin local proximity (e.g., at a same site) to the DS processing unit16 and/or the user device 14, and wherein the DS units 36 of the remoteDSN memory 23 are deployed at one or more sites not within localproximity (e.g., not at the same site) to the DS processing unit 16and/or the user device 14. User device 14 includes a computing core 26,wherein the computing core 26 includes a RAID controller 106.Alternatively, or in addition to, the user device 14 may include a DSprocessing as discussed with reference to FIG. 6A. The RAID controller106 stores RAID data 108 in the RAID memory 102 and/or RAID data 110 inthe local DSN memory 22 and/or remote DSN memory 23 via the DSprocessing unit 16.

The DS processing unit 16 facilitates at least three primary functionsof the system. In a first primary function, the DS processing unit 16facilitates storing RAID data 110 as encoded data slices 11 in the localDSN memory 22 and/or the remote DSN memory 23 (e.g., in response to aRAID data storage request from the RAID controller 106). In a secondprimary function, the DS processing unit 16 facilitates retrieving theencoded data slices 11 from the local DSN memory 22 and/or the remoteDSN memory 23, dispersed storage error decoding encoded slices toproduce RAID data, and sending the RAID data 110 to the RAID controller106 (e.g., in response to a RAID data retrieval request from the RAIDcontroller 106). In a third primary function, the DS processing unit 16facilitates copying (e.g., backing up) RAID data 112 from the RAIDmemory 102 as encoded data slices 11 in the local DSN memory 22 and/orthe remote DSN memory 23.

In an example of a data storing operation, the DS processing unit 16receives RAID data 110 from the RAID controller 106, wherein the RAIDdata 110 includes a store RAID data command. The DS processing unit 16determines which DSN memories to utilize based on matching storagerequirements to the storage capabilities of the local and/or remote DSNmemories 22-23. The DS processing unit 16 saves the selected memorylocation as a DSN memory indicator for subsequent use in a retrievalscenario. Next, the DS processing unit 16 determines a DS method. The DSprocessing unit 16 creates encoded data slices of the RAID data inaccordance with the DS method. The DS processing unit 16 sends theencoded data slices with a store command to the local and/or remote DSNmemories 22-23 for storage therein. The method to create encoded dataslices based on the RAID data is discussed in greater detail withreference to FIG. 12.

In an example of data retrieval operation, the DS processing unit 16receives RAID data 110 from the RAID controller 106, wherein the RAIDdata 110 includes a retrieve RAID data command. The DS processing unit16 determines the DSN memory locations of encoded data slicescorresponding to the requested RAID data based on where the desiredencoded data slices were stored as indicated by the DSN memoryindicator. The DS processing unit 16 determines which of the DSN memorylocations to utilize based on one or more of the DSN memory locations ofthe encoded data slices, retrieval requirements, and DSN memorycapabilities. The DS processing unit 16 retrieves the encoded dataslices from the local DSN memory 22 and/or remote DSN memory 23 anddetermines the DS method. The DS processing unit 16 recovers RAID datafrom the retrieved encoded data slices in accordance with the DS method.The DS processing unit 16 sends the RAID data 110 to the RAID controller106.

In an example of a data copying operation, the DS processing unit 16sends RAID data 112 (e.g., including a retrieve RAID data command) tothe RAID memory 102 to retrieve stored RAID data from the RAID memory102. Note that the DS processing unit 16 communicates with the RAIDmemory 102 utilizing RAID commands as utilized by the RAID controller106 to access the RAID memory 102. Next, the DS processing unit 16receives RAID data 112 from the RAID memory 102. The DS processing unit16 dispersed storage error encodes data of the RAID data 112 to produceencoded data slices. Next, the DS processing unit 16 determines whichDSN memory to utilize based on a comparison of storage requirements toattributes of the DSN memories. The DS processing unit 16 sends theencoded data slices to the DSN memory 22 and/or the DSN memory 23 forstorage therein in accordance with the DSN memory determination. Asanother example of data copying, the DS processing unit 16 retrievesencoded data slices from the DSN memory 22 and/or the DSN memory 23,dispersed storage error decodes the encoded data slices to produce data,transforms the data into RAID data, and sends the RAID data 112 to theRAID memory 102 for storage. As yet another example of data copying, theDS processing unit 16 retrieves the encoded data slices from one of theDSN memory 22 or the DSN memory 23 and stores the encoded data slices inthe other DSN memory. The method to copy and/or backup RAID data isdiscussed in greater detail with reference to FIG. 13.

FIG. 12 is a flowchart illustrating another example of storing data,which includes many similar steps to FIGS. 7 and 10. The method beginswith step 114 of FIG. 7 to receive redundant array of independent disks(RAID) data to store. The method continues with step 138 of FIG. 10 todetermine metadata associated with the RAID data. The method continuesat step 142 where a processing module determines which dispersed storagenetwork (DSN) memory to utilize based on one or more of the metadata,the RAID data, a vault lookup, a command, a message, a predetermination,local DSN memory capabilities, remote DSN memory capabilities, and acomparison of requirements to DSN memory capabilities. For example, theprocessing module determines to utilize a remote DSN memory when aperformance indicator indicates that reliability is favored over lowaccess latency and the remote DSN memory has a high reliabilitycapability. As another example, the processing module determines toutilize a local DSN memory when the performance indicator indicates thatlow access latency is favored over reliability and the local DSN memoryhas a low access latency capability. As yet another example, theprocessing module determines to utilize both the local DSN memory andthe remote DSN memory when the performance indicator indicates that bothlow access latency and high reliability are required and that the localDSN memory has the capability of low access latency and the remote DSNmemory has the capability of high reliability. The method continues withsteps 116, 118, 120, and 122 of FIG. 7 to send the RAID data as encodeddata slices to one or more of the determined DSN memories for storagetherein.

FIG. 13 is a flowchart illustrating another example of copying data,which includes similar steps to FIG. 7. The method begins with step 146where a processing module determines a data object name of a data objectto consider moving and/or deleting. Such a determination may be based onone or more of which data object was most recently considered, a query,a list, a redundant array of independent disks (RAID) data frequency ofaccess indicator, a particular RAID unit, a particular physical memory,a particular RAID memory, an elapsed time since a last retrieval andstorage of same RAID data, a command, a message, a predetermination, avault lookup, and an error message.

The method continues at step 148 where the processing module determinesdata object metadata, wherein the data object metadata may include oneor more of a time indicator to move the data object, an expected accessfrequency indicator, an access frequency threshold, a backup frequencyindicator, an age threshold, a cost indicator, a data type, a data size,a priority indicator, a security indicator, a performance indicator, auser identifier (ID), a group ID, a timestamp, and other descriptors todescribe the data. Such a determination may be based on one or more of avault lookup, a query, a command, a message, a predetermination, anaccess frequency record, a data object name, a data object, a dataobject size, a data type, a data block, parity information, a user ID,RAID unit information, disk drive information, address information,memory information, a command, RAID method information and a request.For example, the processing module determines the data object metadatato include a time indicator to move the data object such that the dataobject should be moved from RAID memory to local DSN memory after 10days from the initial storage to the RAID memory, based on a vaultlookup for the data object.

The method continues at step 150 where the processing module determinesthe data object storage location(s) based on one or more of a memoryindicator, the data object metadata, a vault lookup, a list, a command,a message, a predetermination, local dispersed storage network (DSN)memory capabilities, remote DSN memory capabilities, and a comparison ofrequirements to the DSN memory capabilities. The method continues atstep 152 where the processing module determines if the data objectstorage location(s) compare favorably with the data object metadata. Forexample, the processing module determines if the data object storagelocations still meet the requirements for storage of the data object. Asa specific example, the processing module determines a favorablecomparison when the storage locations still meet the requirements of thedata object in regards to access latency of under 100 ms.

As yet another specific example, the processing module determines anunfavorable comparison when the storage locations do not meet therequirements of the data object with regards to storage reliability oftwelve nines further requiring that the data object be moved to one ormore other storage locations (e.g., moving the data from one memory typeto another memory type). In an instance, the processing moduledetermines that the comparison is unfavorable when the access frequencyis below an access frequency threshold such that it is no longerrequired that the data object be stored in the RAID memory. In anotherinstance, the processing module determines that the comparison isunfavorable when the performance requirement no longer includes thelatency delivered by the RAID memory and/or the local DSN memory but thehigh reliability of the remote DSN memory is still required. The methodrepeats back to step 146 when the processing module determines that thedata object storage location(s) compares favorably with the data objectmetadata. The method continues to step 154 when the processing moduledetermines that the data object storage location(s) do not comparefavorably with the data object metadata.

The method continues at step 154 where the processing module determineswhether to move the data from at least one memory type to at least oneof another memory type based on one or more of the data object, the dataobject metadata, the data object storage locations, storagerequirements, capabilities of the RAID memory, capabilities of the localDSN memory, capabilities of the remote DSN memory, the comparison of thedata object storage locations to the data object metadata, a comparisonof the storage requirements to the memory capabilities, a vault lookup,a list, a predetermination, a command, a message, a query, and/or anerror message. For example, the processing module determines to move thedata object from the RAID memory to the local DSN memory when the localDSN memory provides the required performance at a cost lower than theRAID memory. As a specific example, the processing module determines tomove all RAID blocks of all of the RAID data of all of the data objectsstored in the RAID memory to the local and/or remote DSN memory when theprocessing module determines that the RAID memory is failing too oftenas indicated by the memory performance indicator, or is too costly,and/or if the local and/or remote DSN memory meets the storagerequirements of all of the data objects.

As another example, the processing module determines to move the dataobject from the local DSN memory to the remote DSN memory when theremote DSN memory meets the performance requirements at a lower costthan the local DSN memory. As yet another example, the processing moduledetermines to move the data object from the remote DSN memory to theRAID memory when the frequency of access and latency performancerequirements have become more stringent and are met by the RAID memoryeven though the cost is higher than continuing to utilize the remote DSNmemory. The method branches to step 162 when the processing moduledetermines to not move the data. The method continues to step 116 ofFIG. 7 when the processing module determines to move the data.

The method continues with steps 116 and 118 of FIG. 7 to determine a DSmethod and error coded dispersal storage function parameters (e.g.,operational parameters). The method continues at step 156 where theprocessing module retrieves the data as RAID data from the RAID memoryin accordance with the DS method and operational parameters when the DSprocessing previously determined to move data from the RAID memory(e.g., a current storage location of the data object). The processingmodule retrieves data as encoded data slices from a DSN memory inaccordance with the DS method and operational parameters when theprocessing module previously determined to move data from one of thelocal DSN memory and/or the remote DSN memory (e.g., a current storagelocation of the data object).

The method continues at step 158 where the processing module transformsthe data when the processing module determines to move the data from onetype of memory to another type of memory. For example, the processingmodule transforms RAID data to encoded data slices by dispersed storageerror encoding the RAID data to produce the encoded data slices when theprocessing module determines to move data from the RAID memory to thelocal DSN memory. As another example, the processing module transformsthe encoded data slices to RAID data by dispersed storage error decodingthe encoded data slices to produce the RAID data when the processingmodule determines to move data from the remote DSN memory to the RAIDmemory. As yet another example, the processing module transforms encodeddata slices from a first set of operational parameters to encoded dataslices utilizing a second set of operational parameters when theprocessing module determines to move encoded data slices from the localDSN memory to the remote DSN memory utilizing a different set ofoperational parameters.

The method continues at step 160 where the processing module stores thedata in the memory that the processing module determined to move thedata to. For example, the processing module sends the encoded dataslices created based on the RAID data from the RAID memory with a storeslice command to the local DSN memory to store the encoded data slicesin the local DSN memory. As another example the processing module sendsRAID blocks of the RAID data created based on the encoded data slicesfrom the remote DSN memory with a store RAID data command to the RAIDmemory to store the RAID data in the RAID memory.

The method continues at step 162 where the processing module determineswhether to delete data based on to the results of the previous movedetermination, the data object, the data object metadata, the dataobject storage locations, storage requirements, capabilities of the RAIDmemory, capabilities of the local DSN memory, capabilities of the remoteDSN memory, the comparison of the data object storage locations to thedata object metadata, a comparison of the storage requirements to thememory capabilities, a vault lookup, a list, a predetermination, acommand, a message, a query, and an error message. For example, theprocessing module determines to delete the data object from the RAIDmemory when the processing module determines that the local DSN memoryprovides the required performance at a cost lower than the RAID memoryand when the data object has been stored in the local DSN memory.

As another example, the processing module determines to delete the dataobject from the local DSN memory (e.g., deleting encoded data slices)when the processing module determines that the remote DSN memory meetsthe performance requirements at a lower cost than the local DSN memoryand the data object has been moved to the remote DSN memory. As yetanother example, the processing module determines to delete the dataobject from the remote DSN memory when the processing module determinesthat the frequency of access and latency performance requirements havebecome more stringent and are met by the RAID memory even though thecost is higher than continuing to utilize the remote DSN memory and thedata object has been moved to the RAID memory. The method repeats backto step 146 when the processing module determines to not delete data.The method continues to step 164 where the processing module deletes thedata from at least one memory when the processing module determines todelete data. The processing module deletes RAID blocks of the RAID datain the RAID memory corresponding to the data object, encoded data slicesfrom the local DSN memory, and encoded data slices from the remote DSNmemory. For example, the processing module executes the deletion bysending a delete data command to the memory. The method repeats back tostep 146 where the processing module determines the next data object toconsider moving or deleting.

FIG. 14 is a schematic block diagram of another embodiment of acomputing system that includes at least one user device 14, at least oneredundant array of independent disks (RAID) memory 102, at least onedispersed storage (DS) processing unit 16, and at least one dispersedstorage network (DSN) memory 22. Note that the DSN memory 22 includes aplurality of DS units 36, wherein the DS units 36 may be deployed at oneor more sites. User device 14 includes a computing core 26, wherein thecomputing core 26 includes a RAID controller 106. Alternatively, or inaddition to, the user device 14 may include a DS processing as discussedwith reference to FIG. 6A. The RAID memory 102 includes a plurality ofRAID units 104. The RAID controller 106 stores a portion of RAID data108 in the RAID memory 102 as RAID data 166 via the DS processing unit16 and/or a portion of RAID data 110 in the DSN memory 22 via the DSprocessing unit 16.

The DS processing unit 16 facilitates at least three primary functionsof the system. In a first primary function, the DS processing unit 16facilitates storing RAID data 108 as encoded data slices 11 in the DSNmemory 22 (e.g., in response to a RAID data storage request from theRAID controller 106) and/or as RAID data 166 in the RAID memory 102. Ina second primary function, the DS processing unit 16 facilitatesretrieving the encoded data slices 11 from the DSN memory 22 anddispersed storage error decoding the encoded data slices to producerecovered RAID data, and/or retrieving RAID data 166 from the RAIDmemory 102 to produce retrieved data. Next, the processing module sendsthe recovered RAID data and/or the retrieved RAID data as the RAID data108 to the RAID controller 106 (e.g., in response to a RAID dataretrieval request from the RAID controller 106). In a third primaryfunction, the DS processing unit 16 facilitates migrating data betweenthe RAID memory 102 and the DSN memory 22.

In an example of a data storing operation, the DS processing unit 16receives RAID data 108 from the RAID controller 106, wherein the RAIDdata 108 includes a store RAID data command. The DS processing unit 16determines which memories to utilize based on matching storagerequirements to the storage capabilities of the RAID memory 102 and theDSN memory 22. The DS processing unit 16 saves the selected memorylocation as a memory indicator for subsequent use in a retrievalscenario. Next, the DS processing unit 16 determines a DS method whenstoring a portion of the RAID data 108 as encoded data slices. The DSprocessing unit 16 creates encoded data slices of the RAID data inaccordance with the DS method when storing a portion of the RAID data108 as encoded data slices. The DS processing unit 16 sends the encodeddata slices with a store command to the DSN memory for storage therein.The DS processing unit 16 stores at least a portion of the RAID data 108as RAID data 166 in the RAID memory 102 when storing another portion ofthe RAID data 108 as RAID data. The method to store RAID data isdiscussed in greater detail with reference to FIGS. 15, 18, and 20A.

In an example of a data retrieval operation, the DS processing unit 16receives RAID data 108 from the RAID controller 106, wherein the RAIDdata 108 includes a retrieve RAID data request. The DS processing unit16 determines the memory locations of data associated with the retrieveRAID data request. For example, the processing module determines theencoded data slices 11 stored in the DSN memory 22 corresponding to aportion of the requested RAID data based on where the desired datastored as indicated by the memory indicator. The DS processing unit 16retrieves the encoded data slices from the DSN memory 22 when the DSNmemory 22 stores at least a portion of the requested data. Next, the DSprocessing unit 16 determines the DS method and recovers RAID data fromthe retrieved encoded data slices in accordance with the DS method toproduce recovered RAID data. The DS processing unit 16 retrieves aportion of the RAID data as retrieved RAID data 166 from the RAID memory102 when the processing module determines that a portion of requesteddata is stored in the RAID memory 102. Next, the DS processing unit 16aggregates the recovered RAID data from the DSN memory 22 and theretrieved RAID data from the RAID memory 102 to produce RAID data. TheDS processing unit 16 sends the RAID data as RAID data 108 to the RAIDcontroller 106 in response to the RAID data retrieval request. Themethod to retrieve RAID data is discussed in greater detail withreference to FIGS. 16, 19, and 21.

In an example of a data migration operation, the DS processing unit 16sends RAID data 166 (e.g., including a retrieve RAID data request) tothe RAID memory 102 to retrieve stored RAID data from the RAID memory102 when the DS processing unit 16 determines to migrate RAID data fromthe RAID memory 102 to the DSN memory 22 as encoded data slices. Next,the DS processing unit 16 receives RAID data 166 from the RAID memory102. The DS processing unit 16 dispersed storage error encodes data ofthe RAID data 166 to produce encoded data slices. Next, the DSprocessing unit 16 sends the encoded data slices to the DSN memory 22for storage therein. As another example of data migration, the DSprocessing unit 16 retrieves encoded data slices from the DSN memory 22,dispersed storage error decodes the encoded data slices to produce data,transforms the data into RAID data, and sends the RAID data 166 to theRAID memory 102 for storage therein. As yet another example of datamigration, the DS processing unit 16 retrieves the RAID data 166 fromthe RAID memory 102, dispersed storage error encodes the RAID data toproduce encoded data slices, and sends the encoded data slices to RAIDmemory 102 for storage therein. The method to migrate RAID data isdiscussed in greater detail with reference to FIG. 20B.

In an example of rebuilding RAID data, the DS processing unit 16 sends aRAID data request command to the RAID memory 102 to retrieve RAID data166 from the RAID memory 102. The DS processing unit 16 receives theretrieved RAID data 166 from the RAID memory 102 and determines if theRAID data 166 has errors based on comparing stored parity informationwith calculated parity information of the retrieved RAID data 166. TheDS processing unit 16 rebuilds the RAID data 166 and stores the rebuiltRAID data as RAID data 166 in the RAID memory 102 when the DS processingunit 16 determines that the retrieved RAID data 166 has one or moreerrors and when the errors are correctable based on RAID parity data. Asa specific example, the DS processing unit 16 creates the rebuilt RAIDdata based on the data and parity information retrieved from the RAIDmemory 102. As another specific example, the DS processing unit 16creates the rebuilt RAID data based on RAID data recovered fromretrieved encoded data slices from the DSN memory 22 when the encodeddata slices correspond to the RAID data (e.g., a backup copy). Themethod to rebuild RAID data is discussed in greater detail withreference to FIG. 17.

FIG. 15 is a flowchart illustrating another example of storing data,which includes many similar steps to FIGS. 7 and 10. The method beginswith step 114 of FIG. 7 to receive redundant array of independent disks(RAID) data to store and continues with step 138 of FIG. 10 to determinemetadata of the RAID data. The method continues at step 168 where aprocessing module determines whether to utilize a dispersed storagenetwork (DSN) memory by determining whether to store the RAID data in atleast one of a RAID format and in a DSN format including storing theRAID data in the RAID format and in the DSN format, storing the RAIDdata in the DSN format only, and storing the RAID data in the RAIDformat only. Such a determination may be based on one or more of themetadata, the RAID data, a vault lookup, a command, a message, apredetermination, DSN memory capabilities, RAID memory capabilities, anda comparison of requirements to RAID memory and DSN memory capabilities.Note that the processing module may save the determination choice in amemory indicator that is stored in one or more of the RAID memory, theDSN memory, and a DSN user vault to facilitate a subsequent retrieval ofthe RAID data.

For example, the processing module determines to utilize the DSN memoryonly when the performance indicator indicates that reliability isfavored over low access latency and the DSN memory has a highreliability capability. As another example, the processing moduledetermines to utilize the RAID memory only when the performanceindicator indicates that low access latency is favored over reliabilityand the RAID memory has a low access latency capability. As yet anotherexample, the processing module determines to utilize both the DSN memoryand the RAID memory when the performance indicator indicates that bothlow access latency and high reliability is required and that the RAIDmemory has the capability of low access latency and the DSN memory hasthe capability of high reliability. The method branches to step 170 whenthe processing module determines to not utilize the DSN memory. Themethod continues to step 116 of FIG. 7 when the processing moduledetermines to utilize the DSN memory.

The method continues with steps 116 and 118 of FIG. 7 when theprocessing module determines to utilize the DSN memory. The methodcontinues with step 120 of FIG. 7 where the processing module dispersedstorage error encodes the RAID data to produce encoded data slices(e.g., a set of encoded data slices, a plurality of sets of encoded dataslices). As a specific example, the processing module converts at leasta portion of the RAID data into at least one set of encoded data sliceswhen at least a portion of the RAID data is to be stored in the DSNformat. As another specific example, the processing module converts theRAID data into a plurality of sets of encoded data slices. The methodcontinues with step 122 of FIG. 7 where the processing module outputs(e.g., sends) the encoded data slices to the DSN memory for storagetherein. Alternatively, the processing module outputs at least one setof the plurality of sets of encoded data slices to the DSN memory andoutputs at least one other set of the plurality of sets of encoded dataslices to a RAID memory. Alternatively, or in addition to, theprocessing module converts the at least one other set of the pluralityof sets of encoded data slices into the RAID format prior to outputtingto the RAID memory. In yet another alternative processing module outputsa sub-set of each of the plurality of sets of encoded data slices to theDSN memory and outputs remaining encoded data slices of each of theplurality of sets of encoded data slices to a RAID memory.

The method continues at step 170 where the processing module determineswhether to utilize the RAID memory based on a previous memorydetermination. The method branches to an end at step 160 when theprocessing module determines to not utilize the RAID memory. The methodcontinues to step 172 when the processing module determines to utilizethe RAID memory. The method continues at step 172 where the processingmodule outputs the RAID data to the RAID memory (e.g., forwarding atleast a portion of the RAID data to the RAID memory to store the RAIDdata in the RAID memory, converting encoded data slices into RAID dataand sending the RAID data to the RAID memory). Alternatively, or inaddition to, the processing module determines whether to convert theRAID data from a first RAID format to a second RAID format when aremaining portion of the RAID data is to be stored in the RAID formatand converting the RAID data from the first RAID format to the secondRAID format when the RAID data is to be converted from the first RAIDformat to the second RAID format. Such a determination may be based onone or more of a storage requirement and a RAID memory capability.

FIG. 16 is a flowchart illustrating another example of retrieving data,which includes many similar steps to FIGS. 7, 8, and 10. The methodbegins with step 124 of FIG. 8 to receive a redundant array ofindependent disks (RAID) data request from a requester and continueswith step 138 of FIG. 10 to determine metadata. The method continues atstep 174 where a processing module determines which memory to try toretrieve the RAID data from (e.g., determining whether to retrieve theRAID data from at least one of a RAID memory and a dispersed storagenetwork (DSN) memory). Such a determination may include determiningformatting of storing the RAID data and determining to retrieve the RAIDdata from the RAID memory based on a desired retrieval speed. Thedetermination may based on one or more of the metadata, a memoryindicator, the RAID data, a vault lookup, a command, a message, apredetermination, DSN memory capabilities, RAID memory capabilities, anda comparison of requirements to the RAID memory and DSN memorycapabilities.

For example, the processing module determines to retrieve from the DSNmemory when the performance indicator indicates that reliability isfavored over low access latency and the DSN memory has a highreliability capability and includes the desired RAID data. As anotherexample, the processing module determines to retrieve from the RAIDmemory when the performance indicator indicates that low access latencyis favored over reliability and the RAID memory has a low access latencycapability and includes the desired RAID data. As yet another example,the processing module determines to retrieve from both the DSN memoryand the RAID memory when the performance indicator indicates that bothlow access latency and high reliability is required and that the RAIDmemory has the capability of low access latency and the DSN memory hasthe capability of high reliability and further when the RAID memory hasa failure in the retrieval process. The method continues at step 176where the processing module determines whether to retrieve from the RAIDmemory based on the memory determination of step 174. The methodbranches to step 184 when the processing module determines not toretrieve from the RAID memory. The method continues to step 178 when theprocessing module determines to retrieve from the RAID memory.

The method continues at step 178 where the processing module forwardsthe RAID data request to the RAID memory to retrieve the RAID data fromthe RAID memory. Next, at step 180, the processing module receives theRAID data. Alternatively, the processing module retrieves a remainingportion of the RAID data from the RAID memory (e.g., when a portion ofthe RAID data is stored as encoded data slices) and merges the remainingportion of the RAID data with the at least a portion of the RAID data toproduce the RAID data. Next, at step 180, the processing moduledetermines whether the received RAID data is valid based on comparingstored parity information to calculated parity information. Theprocessing module determines that the received RAID data is valid whenthe calculated parity information is substantially the same as thestored parity information. The method ends with step 130 of FIG. 8 whenthe processing module determines that the RAID data is valid. The methodcontinues to step 182 when the processing module determines that theRAID data is not valid. The method continues at step 182 where theprocessing module sends a RAID failure message to one or more of a RAIDcontroller, a DS managing unit, and a user device, wherein the RAIDfailure message indicates that the RAID data is not valid and may not becorrectable utilizing only data stored within the RAID memory. Themethod branches to step 184. Note that the DSN memory may contain abackup copy of the data of the requested RAID data.

The method continues at step 184 where the processing module determineswhether to retrieve data from the DSN memory based on the previousmemory determination and/or when retrieved RAID data from the RAIDmemory is not valid and not correctable. For example, the processingmodule determines to retrieve data from the DSN memory when the desireddata exists in the DSN memory and attempted retrieval of the data fromthe RAID memory resulted in RAID data that was not valid. As anotherexample, the processing module determines to retrieve the data from theDSN memory when the data was not previously stored in the RAID memoryand when data was previously stored in the DSN memory. The method endsat step 186 when the processing module determines to not read data fromthe DSN memory. The method continues to step 118 of FIG. 7 when theprocessing module determines to read data from the DSN memory.

The method continues with step 118 of FIG. 7 to determine error codingdispersal storage function parameters. The method continues with step126 of FIG. 8 to retrieve encoded data slices from the DSN memory. Themethod continues with step 116 of FIG. 7 to determine a dispersedstorage (DS) method. The method continues with step 128 of FIG. 8 tore-create RAID data from the encoded data slices. Note that theprocessing module converts at least one set of encoded data slices intoat least a portion of the RAID data when at least a portion of the RAIDdata is to be retrieved from the DSN memory. The method continues withstep 130 of FIG. 8 to send RAID data to the requester. Note that theprocessing module outputs the at least a portion of the RAID data whenretrieving the at least the portion of the RAID data from the DSNmemory.

FIG. 17 is a flowchart illustrating another example of rebuilding data,which includes many similar steps to FIGS. 7, 8, and 9B. The methodbegins with steps 132-134 of FIG. 9B to retrieve redundant array ofindependent disks (RAID) data for rebuilding consideration and thencontinues with step 188 where a processing module determines whether theRAID data has errors. Such a determination includes comparing storedparity to calculated parity of the RAID data. For example, theprocessing module determines that the RAID data does not have errorswhen the stored parity is substantially the same as the calculatedparity of the RAID data. The method repeats back to step 132 where theprocessing module determines the next portion of the RAID data toretrieve and consider for rebuilding when the processing moduledetermines that the RAID data does not have errors. The method continuesto step 190 when the processing module determines that the RAID data haserrors.

The method continues at step 190 where the processing module determineswhether the RAID data errors are correctable with RAID data from RAIDmemory. For example, the processing module determines that the RAID dataerrors are correctable when there are sufficient good RAID block datablocks and RAID parity data blocks to re-create the original data inaccordance with a RAID method. The method branches to the step 116 ofFIG. 7 when the processing module determines that the RAID data errorsare not correctable with the RAID data. Note that in this scenario theprocessing module attempts to rebuild the uncorrectable RAID data byretrieving a backup copy of the data from a dispersed storage network(DSN) memory. The method continues to step 192 when the processingmodule determines that the RAID data errors are correctable with theRAID data. The method continues at step 192 where the processing modulecorrects the RAID data errors utilizing RAID data in accordance with theRAID method storing corrected RAID data in the RAID memory

The method continues with steps 116-118 of FIG. 7 and then continueswith steps 126-128 of FIG. 8 to produce re-created RAID data fromencoded data slices retrieved from the DSN memory. The method continuesat step 194 where the processing module stores the re-created RAID datain the RAID memory by sending the RAID data to the RAID memory with astore command.

FIG. 18 is a flowchart illustrating another example of storing data,which includes many similar steps to FIGS. 7 and 10. The method beginswith step 114 of FIG. 7 to receive redundant array of independent disks(RAID) data to store and then continues with step 138 of FIG. 10 todetermine metadata of the RAID data. The method continues with step 116of FIG. 7 to determine a dispersed storage (DS) method. For example, theprocessing module determines the DS method to utilize a dispersedstorage network (DSN) memory only when a performance indicator indicatesthat reliability is favored over low access latency and the DSN memoryhas a high reliability capability. As another example, the processingmodule determines the DS method to utilize a RAID memory only when theperformance indicator indicates that low access latency is favored overreliability and the RAID memory has a low access latency capability.

As yet another example, the processing module determines the DS methodto utilize both the DSN memory and the RAID memory when the performanceindicator indicates that both low access latency and high reliability isrequired and that the RAID memory has the capability of low accesslatency and the DSN memory has the capability of high reliability. Notethat the DS method may further describe a number of pillars to be storedin which type of memory. For example, the processing module determinesthe DS method to encode and store a decode threshold k number of encodeddata slices in the DSN memory and n−k encoded data slices in the RAIDmemory. Alternatively, or in addition to, the DS method furtherdescribes DS units that are included in a DS unit storage set within theDSN memory.

The method continues with steps 118-120 of FIG. 7 where a processingmodule encodes the RAID data to produce a set of n pillars of encodeddata slices. The method continues with step 196 where the processingmodule determines portions of the n pillar slices based on the DS method(e.g., how many and which pillars to send to which memory type). Notethat a performance improvement may be provided to the system when thefirst k pillars are the same as the data (e.g., when an encoding matrixthat includes a unity matrix is utilized to produce the encoded dataslices). The method continues at step 198 where the processing modulesends a first portion of encoded data slices to the DSN memory to storethe first portion of pillar slices in the DSN memory. For example, theprocessing module outputs at least one set of the plurality of sets ofencoded data slices to the DSN memory. The method continues at step 200where the processing module creates auxiliary RAID data from a secondportion of encoded data slices in accordance with the DS method. Forexample, the processing module converts at least one other set of theplurality of sets of encoded data slices into a RAID format prior tooutputting. The method continues at step 202 where the processing modulesends the auxiliary RAID data to the RAID memory with a store command tostore the second portion of encoded data slices as auxiliary RAID datain the RAID memory. For example, the processing module outputs at leastone other set of the plurality of sets of encoded data slices in theRAID format to the RAID memory.

FIG. 19 is a flowchart illustrating another example of retrieving data,which includes similar steps to FIGS. 8 and 10. The method begins withstep 124 of FIG. 8 to receive a RAID data request from a requester andthen continues with step 138 of FIG. 10. The method continues with steps116-118 of FIG. 7 and then continues with step 204 where a processingmodule retrieves a first portion of encoded data slices from a dispersedstorage network (DSN) memory based in part on one or more of DSN storagelocation information, a storage method, and error coding dispersalstorage function parameters (e.g., operational parameters). Note thatthe method repeats for each data segment of a plurality of data segmentsassociated with a data object of the RAID data request. Further notethat it is possible to decode each of the plurality of data segments ofthe data object when a read threshold number of encoded data slices aresuccessfully retrieved for each data segment. As such, the requestedRAID data can be re-created when each of the data segments of the dataobject is successfully re-created.

The method continues at step 206 where the processing module determineswhether the requested RAID data can be re-created based on determiningwhether a read threshold number of encoded data slices were retrievedfor all data segments. Note that there can be no missing pillars inorder to successfully re-create the data object based solely on theslices retrieved from the DSN memory when the storage method indicatesthat exactly a read threshold number of pillars were stored in the DSNmemory. The method branches to step 128 of FIG. 8 when the processingmodule determines that the requested RAID data can be re-created. Themethod continues to step 208 when the processing module determines thatthe requested RAID data can't be re-created so far.

The method continues at step 208 where the processing module sends anauxiliary RAID data request to a RAID memory to retrieve a secondportion of encoded data slices. For example, the processing moduleretrieves the other n−k pillars in an attempt to successfully decode apreviously un-decodable data segment. As another example, the processingmodule requests auxiliary RAID data corresponding to pillar slices forthe data segments where there are not a read threshold number ofretrieved pillars slices so far. The method continues at step 210 wherethe processing module receives the auxiliary RAID data from the RAIDmemory. Next, the processing module dispersed storage error encodes theauxiliary RAID data into a second portion of encoded data slices.

The method continues at step 212 where the processing module determineswhether the requested RAID data can be re-created when a favorablecomparison of a total number of required data segments compared to anumber of data segments of at least a read threshold number of pillarshave been received. For example, the processing module determines thatthe requested RAID data can be re-created when at least a decodethreshold number of pillar slices have been received for each datasegment of a plurality of data segments required to re-create the RAIDdata. The method ends at step 214 when the processing module determinesthat the requested RAID data can't be re-created. At step 214, theprocessing module sends a failure message to the requester and/or to aDS managing unit. The method continues to step 128 of FIG. 8 when theprocessing module determines that the requested RAID data can bere-created. The method continues with steps 128-130 of FIG. 8 tore-create RAID data from the encoded data slices and send the RAID datato the requester.

FIG. 20A is a flowchart illustrating another example of storing of data,which includes many similar steps to FIGS. 7, 10, and 18. The methodbegins with step 114 of FIG. 7 to receive RAID data to store and thenwith step 138 of FIG. 10. The method continues with step 116 of FIG. 7to determine a dispersed storage (DS) method. The method continues atstep 216 where a processing module partitions the RAID data into atleast a first RAID partition and a second RAID partition in accordancewith the DS method. For example, the processing module partitions 100%of the RAID data to the first RAID partition associated with a RAIDmemory when the RAID memory is much faster than a dispersed storagenetwork (DSN) memory associated with the second RAID partition and astorage requirement indicates that fast retrieval is more important thanreliability. As another example, the processing module partitions theRAID data such that the first RAID partition includes 50% of the RAIDdata and the second RAID partition includes 50% of the RAID data whenthe capacity of the RAID memory is below a RAID memory threshold. Notethat this may be an interim step to migrate storage of data from theRAID memory to the DSN memory. As yet another example, the processingmodule partitions the RAID data such that the first RAID partitionincludes 0% of the RAID data and the second RAID partition includes 100%of the RAID data when the storage requirement indicates to providehigher reliability by fully utilizing the DSN memory.

The method continues at step 218 where the processing module sends RAIDdata of the first RAID partition with a store command to a RAID memoryto store the RAID data of the first RAID partition in the RAID memory.The method continues at step 118 of FIG. 7 to determine error codingdispersal storage function parameters (e.g., operational parameters).The method continues at step 220 where the processing module dispersedstorage error encodes RAID data of the second RAID partition to producen pillars of encoded data slices in accordance with the error codingdispersal storage function parameters and the DS method. The methodcontinues with steps 196-202 of FIG. 18.

FIG. 20B is a flowchart illustrating an example of migrating data, whichincludes steps similar to FIGS. 8 and 10. The method begins with step222 where a processing module determines whether to convert data betweena redundant array of independent disks (RAID) format and a dispersedstorage network (DSN) format. Such a determination includes at least oneof determining when an access frequency of the data compares favorablyto an access threshold, determining when an access speed for the datacompares favorably to an access speed threshold, determining when acapacity of the RAID memory compares favorably to a capacity threshold,and receiving a data conversion command. For example, the processingmodule determines to convert data from the RAID format to the DSN formatwhen the capacity of the RAID memory compares favorably to a capacitythreshold (e.g., the capacity of the RAID memory falls below thecapacity threshold).

As another example, the processing module determines to convert datafrom the RAID format to the DSN format when the access frequency of thedata compares favorably to the access threshold (e.g., the accessfrequency for the data is substantially less than the access threshold).As yet another example, the processing module determines to convert datafrom the DSN format to the RAID format when the access speed for thedata compares favorably to the access speed threshold (e.g., accessspeed for the data is below the access speed threshold). The methodrepeats at step 222 when the processing module determines not to convertdata between the RAID format and the DSN format.

The method branches to step 126 of FIG. 8 when the processing moduledetermines to convert DSN format data to RAID format data. The methodcontinues to step 134 of FIG. 9B when the processing module determinesto convert RAID format data to DSN format data.

The method continues with step 134 of FIG. 9B where the processingmodule retrieves the RAID data to be converted. The method continues atstep 224 where the processing module converts stripe-block data of theretrieved RAID data into a plurality of sets of encoded data slices. Forexample, the processing module dispersed storage error encodes thestripe-block data to produce the plurality of sets of encoded dataslices, wherein the stripe-block data includes data and replicated dataof the data (e.g., when the RAID format data was produced in accordancewith a RAID method that includes replication such as RAID 1). As anotherexample, the processing module dispersed storage error encodes thestripe-block data to produce the plurality of sets of encoded dataslices, wherein the stripe-block data includes data and excludesreplicated data of the data.

The method continues at step 226 where the processing module outputs theplurality of sets of encoded data slices to at least one of the RAIDmemory and the DSN memory for storage therein. For example, theprocessing module outputs at least one set of the plurality of sets ofencoded data slices to the DSN memory and outputs at least one other setof the plurality of sets of encoded data slices to the RAID memory. Asanother example, the processing module outputs a sub-set of each of theplurality of sets of encoded data slices to the DSN memory and outputsremaining encoded data slices of each of the plurality of sets ofencoded data slices to the RAID memory. Alternatively, or in additionto, the processing module sends an overwrite message to the RAID memorysuch that the RAID memory overwrites the data of the retrieved RAID datawith at least some of the plurality of sets of encoded data slices. Themethod continues at step 228 where the processing module sends a deletedata message to the RAID memory requesting the RAID memory to delete thedata of the RAID data.

The method continues with 126 of FIG. 8 where the processing moduleretrieves the plurality of sets of encoded data slices from the DSNmemory when the processing module determines to convert DSN format datato RAID format data. The method continues at step 230 where theprocessing module decodes the plurality of sets of encoded data slicesto produce recovered DSN data. The method continues at step 232 wherethe processing module converts the DSN data into RAID data. The methodcontinues at step 234 where the processing module outputs the RAID datato the RAID memory.

FIG. 21 is a flowchart illustrating another example of retrieving data,which includes many similar steps to FIGS. 7, 8, 10, and 19. The methodbegins with step 124 of FIG. 8, step 138 of FIG. 10, step 116 of FIG. 7and then continues with step 236 where a processing module retrieves afirst redundant array of independent disks (RAID) data partition from aRAID memory by sending a RAID data request to the RAID memory. Theprocessing module receives the first RAID data partition of RAID data.The method continues with step 118 of FIG. 7 to determine error codingdispersal storage function parameters.

The method continues at step 238 where the processing module retrieves afirst portion of encoded data slices for a second RAID data partition ofRAID data from a dispersed storage network (DSN) memory based on one ormore of DSN storage location information, the storage method, and theerror coding dispersal storage function parameters. Note that the methodrepeats for each of the data segments of the data object. Further notethat it is possible to decode each of the data segments of the dataobject when a read threshold number of encoded data slices issuccessfully retrieved for each data segment. The requested RAID datacan be re-created when each of the data segments of the data object issuccessfully re-created.

The method continues with step 206 of FIG. 19 to determine whetherrequested RAID data can be re-created. The method branches to step 242when the processing module determines that the requested RAID data canbe re-created. The method continues to step 240 when the processingmodule determines that the requested RAID data can't be re-created sofar. The method continues at step 240 where the processing module sendsan auxiliary RAID data request to the RAID memory to retrieve a secondportion of encoded data slices of a second partition of RAID data. Forexample, the processing module retrieves other n−k pillars in an attemptto successfully decode a previously un-decodable data segment. Note thatthe processing module requests auxiliary RAID data corresponding to thepillar slices for the data segments where a decode threshold number ofretrieved pillars slices have not been received so far. The methodcontinues at step 210 of FIG. 19 to receive the auxiliary RAID data fromthe RAID memory. The processing module dispersed storage error encodesthe auxiliary RAID data into the second portion of encoded data slicesthat is part of the second partition of RAID data. The method continuesat step 206 of FIG. 19 to determine whether the requested RAID data canbe re-created. The method ends at step 214 of FIG. 19 sending a failuremessage when the processing module determines that the requested RAIDdata can't be re-created. The method continues to step 242 when theprocessing module determines that the requested RAID data can bere-created.

The method continues at step 242 where the processing module recreatesthe second partition of RAID data based on dispersed storage errordecoding the retrieved encoded data slices in accordance with the errorcoding dispersal storage function parameters and a DS method. The methodcontinues at step 244 where the processing module aggregates the firstRAID data partition and the second RAID data partition to produce therequested RAID data. The method continues with step 130 of FIG. 8 wherethe processing module sends the RAID data to the requester.

FIG. 22 is a schematic block diagram of another embodiment of acomputing system that includes at least one user device 14, at least oneredundant array of independent disks (RAID) memory 102, at least onedispersed storage (DS) processing unit 16, at least one local dispersedstorage network (DSN) memory 22, and at least one remote DSN memory 23.Note that the local DSN memory 22 and the remote DSN memory 23 include aplurality of dispersed storage (DS) units 36, wherein the DS units 36 ofthe local DSN memory 22 are deployed at one or more sites within localproximity (e.g., at a same site) to the DS processing unit 16 and/or theuser device 14, and wherein the DS units 36 of the remote DSN memory 23are deployed at one or more sites not within local proximity (e.g., notat the same site) to the DS processing unit 16 and/or the user device14. User device 14 includes a computing core 26, wherein the computingcore 26 includes a RAID controller 106. Alternatively, or in additionto, the user device 14 may include a DS processing as discussed withreference to FIG. 6A. The RAID memory 102 includes a plurality of RAIDunits 104. The RAID controller 106 stores RAID data 108 in the RAIDmemory 102 as RAID data 166 via the DS processing unit 16 and/or RAIDdata 108 in the local DSN memory 22 and/or remote DSN memory 23 via theDS processing unit 16 as encoded data slices 11.

The DS processing unit 16 facilitates at least three primary functionsof the system. In a first primary function, the DS processing unit 16facilitates storing RAID data 108 as encoded data slices 11 in the localDSN memory 22 and/or remote DSN memory 23 (e.g., in response to a RAIDdata storage request from the RAID controller 106) and/or as RAID data166 in the RAID memory 102. In a second primary function, the DSprocessing unit 16 facilitates retrieving the encoded data slices 11from the local DSN memory 22 and/or the remote DSN memory 23 anddispersed storage error decoding encoded slices to produce recoveredRAID data, and/or retrieving RAID data 166 from the RAID memory 102 toproduce retrieved RAID data. Next, the processing module sends therecovered RAID data and/or the retrieved RAID data as the RAID data 108to the RAID controller 106 (e.g., in response to a RAID data retrievalrequest from the RAID controller 106). In a third primary function, theDS processing unit 16 facilitates migrating data between any of the RAIDmemory 102, the local DSN memory 22, and the remote DSN memory 23.

In an example of a data storing operation, the DS processing unit 16receives RAID data 108 from the RAID controller 106, wherein the RAIDdata 108 includes a store RAID data command. The DS processing unit 16determines which memories to utilize based on matching storagerequirements to the storage capabilities of the RAID memory 102, thelocal DSN memory 22, and the remote DSN memory 23. The DS processingunit 16 saves the selected memory location as a memory indicator forsubsequent use in a retrieval scenario. Next, the DS processing unit 16determines a DS method when storing a portion of the RAID data 108 asencoded data slices. The DS processing unit 16 creates encoded dataslices of the RAID data in accordance with the DS method when storing aportion of the RAID data 108 as encoded data slices. The DS processingunit 16 determines which of the local DSN memory 22 and the remote DSNmemory 23 to utilize when storing encoded data slices in a DSN memory.The DS processing unit 16 sends the encoded data slices with a storecommand to the local DSN memory 22 and/or the remote DSN memory 23 forstorage therein. The DS processing unit 16 stores at least a portion ofthe RAID data 108 as RAID data 166 in the RAID memory 102 when storinganother portion of the RAID data 108 as RAID data. The method to storeRAID data is discussed in greater detail with reference to FIG. 23.

In an example of data retrieval operation, the DS processing unit 16receives RAID data 108 from the RAID controller 106, wherein the RAIDdata 108 includes a retrieve RAID data request. The DS processing unit16 determines the memory locations of data associated with the retrieveRAID data request. For example, the processing module determines theencoded data slices 11 stored in the local DSN memory 22 correspondingto a portion of the requested RAID data based on where the desired datastored as indicated by the memory indicator. The DS processing unit 16retrieves the encoded data slices from the local DSN memory 22 when thelocal DSN memory 22 stores at least a portion of the requested data.Next, the DS processing unit 16 determines the DS method and recoversRAID data from the retrieved encoded data slices in accordance with theDS method to produce recovered RAID data. The DS processing unit 16retrieves a portion of the RAID data as retrieved RAID data 166 from theRAID memory 102 when the processing module determines that a portion ofrequested data is stored in the RAID memory 102. Next, the DS processingunit 16 aggregates the recovered RAID data from the local DSN memory 22and the retrieved RAID data from the RAID memory 102 to produce RAIDdata. The DS processing unit 16 sends the RAID data as RAID data 108 tothe RAID controller 106 in response to the RAID data retrieval request.

In an example of a data migration operation, the DS processing unit 16sends RAID data 166 (e.g., including a retrieve RAID data request) tothe RAID memory 102 to retrieve stored RAID data from the RAID memory102 when the DS processing unit 16 determines to migrate RAID data fromthe RAID memory 102 to the local DSN memory 22 and/or the remote DSNmemory 23 as encoded data slices. Next, the DS processing unit 16receives RAID data 166 from the RAID memory 102. The DS processing unit16 dispersed storage error encodes data of the RAID data 166 to produceencoded data slices. The DS processing unit 16 determines which of thelocal DSN memory 22 in the remote DSN memory 23 to utilize to store theencoded data slices. Next, the DS processing unit 16 sends the encodeddata slices to the local DSN memory 22 and/or the remote DSN memory 23for storage therein. As another example of data migration, the DSprocessing unit 16 retrieves encoded data slices from the remote DSNmemory 23, dispersed storage error decodes the encoded data slices toproduce data, transforms the data into RAID data, and sends the RAIDdata 166 to the RAID memory 102 for storage therein. As yet anotherexample of data migration, the DS processing unit 16 retrieves encodeddata slices from the local DSN memory 22 and sends the encoded dataslices to the remote DSN memory 23 for storage therein.

Alternatively, or in addition to, the DS processing unit 16 maydetermine to delete one or more copies of RAID data from one or more ofthe RAID memory 102, the local DSN memory 22, and/or the remote DSNmemory 23. Such a determination may be based on one or more of an accessfrequency, performance requirements, metadata, costs, and other factorsto optimize the use of all of the memory types.

FIG. 23 is a flowchart illustrating another example of storing data,which includes many similar steps to FIGS. 7, 10, and 15. The methodbegins with step 114 of FIG. 7 where a processing module receivesredundant array of independent disks (RAID) data to store and thencontinues with step 138 of FIG. 10 to determine metadata. The methodcontinues at step 246 where the processing module determines whichmemories to utilize (e.g., a RAID memory, local and/or remote dispersedstorage network (DSN) memory) to utilize based on one or more of themetadata, the RAID data, a vault lookup, a command, a message, aperformance indicator, a predetermination, local DSN memorycapabilities, remote DSN memory capabilities, RAID memory capabilities,and a comparison of requirements to capabilities of the RAID memory andlocal and/or DSN memory. The processing module saves the determinationchoice in a memory indicator that is stored in one or more of the RAIDmemory, the local DSN memory, the remote DSN memory, and a DSN uservault.

For example, the processing module determines to utilize the remote DSNmemory when the performance indicator indicates that reliability isfavored over low access latency and the remote DSN memory has a highreliability capability. As another example, the processing moduledetermines to utilize the local RAID memory when the performanceindicator indicates that low access latency is favored over reliabilityand the local RAID memory has a low access latency capability. As yetanother example, the processing module determines to utilize both thelocal DSN memory and the RAID memory when the performance indicatorindicates that both low access latency and good reliability is requiredand that the RAID memory has the capability of low access latency andthe local DSN memory has the capability of good reliability. The methodbranches to the step 250 when the processing module determines to notutilize the RAID memory. The method continues to step 172 when theprocessing module determines to utilize the RAID memory. The methodcontinues at step 172 of FIG. 15 where the processing module forwardsthe RAID data to the RAID memory.

The method continues at step 250 where the processing module determineswhether to utilize the local DSN memory based on the previous memorydetermination. The method branches to step 256 when the processingmodule determines to not utilize the local DSN memory. The methodcontinues to step 116 of FIG. 7 when the processing module determines toutilize the local DSN memory. The method continues with step 116 of FIG.7 to determine a DS method. The method continues at step 252 where theprocessing module determines local error coding dispersal storagefunction parameters (e.g., operational parameters). Such a determinationmay be based on one or more of a vault lookup, RAID memory configurationinformation, a performance indicator, a command, a message, apredetermination, a data object name, a data object, a data object size,a data type, a data block, parity information, a user ID, RAID unitinformation, disk drive information, address information, memoryinformation, a command, and a request. For example, the processingmodule determines the local error coding dispersal storage functionparameters to include a pillar width of 4 and a decode threshold of 3 toprovide fast performance and moderate reliability in accordance with alocal proximity of an associated local DSN memory. The method continueswith step 120 of FIG. 7 to produce encoded data slices from the RAIDdata. The method continues at step 254 where the processing module sendsthe encoded data slices to the local DSN memory for storage therein.

The method continues at step 256 where the processing module determineswhether to utilize the remote DSN memory based on the previous memorydetermination. The method ends at step 262 when the processing moduledetermines not to utilize the remote DSN memory. The method continues tostep 116 of FIG. 7 when the processing module determines to utilize theremote DSN memory. The method continues with step 116 of FIG. 7 todetermine the DS method. The method continues at step 258 where theprocessing module determines remote error coding dispersal storagefunction parameters (e.g., operational parameters). Such a determinationmay be based on one or more of a vault lookup, local error codingdispersal storage function parameters, RAID memory configurationinformation, a performance indicator, a command, a message, apredetermination, a data object name, a data object, a data object size,a data type, a data block, parity information, a user ID, RAID unitinformation, disk drive information, address information, memoryinformation, a command, and a request. For example, the processingmodule determines the remote error coding dispersal storage functionparameters to include a pillar width of 32 and a decode threshold of 20to provide high reliability in accordance with a remote proximity of anassociated remote DSN memory. The method continues with step 120 of FIG.7 to produce encoded data slices from the RAID data. The methodcontinues at step 260 where the processing module sends the encoded dataslices to the remote DSN memory for storage therein.

FIG. 24 is a schematic block diagram of another embodiment of acomputing system that includes two user devices 14, two redundant arrayof independent disks (RAID) memories 102, two dispersed storage (DS)processing units 16, two local dispersed storage network (DSN) memories22, and one remote DSN memory 23. Note that the system comprises twosubsystems, wherein each subsystem includes the user device 14, the DSprocessing unit 16, the RAID memory 102, and the local DSN memory 22.Further note that each subsystem shares a common remote DSN memory 23,wherein the remote DSN memory 23 is not within local proximity of eithersubsystem. Each subsystem operates as previously discussed withreference to FIG. 14 with regards to storing RAID data 108 as RAID data166 in the RAID memory 102 and as encoded data slices 11 in the localDSN memory 22. Each subsystem operates as previously discussed withreference to FIG. 22 with regards to storing RAID data 108 as encodeddata slices 11 in the local DSN memory 22 or the remote DSN memory 23.

In addition, the DS processing unit 16 facilitates another function ofthe system. Each DS processing unit determines whether to store RAIDdata 108 as encoded data slices 11 in an associated local DSN memory 22or in the common remote DSN memory 23 in accordance with a DSN memoryselection method. Such a DSN memory selection method includesdetermining whether the RAID data 108 includes data that is common toboth subsystems of the system. The DS processing unit 16 stores the RAIDdata 108 as encoded data slices in the remote DSN memory 23 when thedata of RAID data 108 is common to both subsystems, when the data is notalready stored in the remote DSN number 23, and a high level of storagereliability is required. In addition, the DS processing unit 16 storesthe RAID data 108 as encoded data slices 11 in the associated local DSNmemory 22 when a high-performance level of data access is required(e.g., low excess latency, frequent access sequences). The method ofoperation of the DS processing unit 16 is discussed in greater detailwith reference to FIG. 25.

FIG. 25 is a flowchart illustrating another example of storing data,which includes many similar steps to FIGS. 7, 10, 15, and 23. The methodbegins with step 114 of FIG. 7 where a processing module receives RAIDdata to store and then continues with step 138 of FIG. 10 to determinemetadata. The method continues with step 246 of FIG. 23 to determinewhich memories to utilize and then with step 170 of FIG. 15 to determinewhether to utilize a RAID memory. The method branches to step 168 ofFIG. 15 when the processing module determines to not utilize the RAIDmemory. The method continues to step 172 of FIG. 15 when the processingmodule determines to utilize the RAID memory. The method continues withstep 172 of FIG. 15 to forward the RAID data to the RAID memory. Themethod continues with step 168 of FIG. 15 to determine whether toutilize a dispersed storage network (DSN) memory. The method branches tostep 116 of FIG. 7 when the processing module determines to utilize theDSN memory. The method ends at step 262 when the processing moduledetermines not to utilize the DSN memory.

The method continues with steps 116-120 of FIG. 7 where the processingmodule produces encoded data slices from the RAID data. The methodcontinues at step 264 where the processing module sends a decodethreshold k number of pillars of the encoded data slices with a storecommand to a local DSN memory for storage. Note that the decodethreshold number of pillars of encoded data slices stored in the localDSN memory facilitates a subsequent retrieval with a preferred accesslatency.

The method continues at step 266 where the processing module determineshow many pillars of encoded data slices to utilize to store in a remoteDSN memory based on one or more of the metadata, the RAID data, a vaultlookup, a command, a message, a predetermination, memory capabilities,and a comparison of storage requirements to memory capabilities. Theprocessing module saves the outcome of the determination to facilitatesubsequent retrieval of the data. For example, the processing moduledetermines to store a full pillar width n number of encoded data slicesin the remote DSN memory when the remote DSN memory capacity is above acapacity threshold. In another example, the processing module determinesto store the pillar width minus the decode threshold number of pillarslices (n−k) in the remote DSN memory when the processing moduledetermines that a memory utilization indicator of the remote DSN memoryis above a memory utilization threshold. The method branches to step 258of FIG. 23 when the processing module determines to store a pillar widthn number of encoded data slices in the remote DSN memory. The methodends with step 268 where the processing module sends the remainingpillar width minus the decode threshold (n−k) number of encoded dataslices to the remote DSN memory to store the remaining encoded dataslices in the remote DSN memory.

The method continues with step 258 of FIG. 23 to determine remote errorcoding dispersal storage function parameters associated with the remoteDSN memory. The method continues with step 120 of FIG. 7 where theprocessing module dispersed storage error encodes the RAID data toproduce encoded data slices in accordance with the remote error codingdispersal storage function parameters. The method continues with step260 of FIG. 23 where the processing module sends the encoded data slicesto the remote DSN memory for storage therein.

Alternatively, or in addition to, the processing module determineswhether the RAID data is already stored as encoded data slices in theremote DSN memory based on a retrieval of encoded data slices from theremote DSN memory that may correspond to the RAID data and/or acomparison of the retrieved encoded data slices to encoded data slicesgenerated as described above from the RAID data. For example, theprocessing module sends newly created encoded data slices to the remoteDSN memory for storage when the processing module determines that theRAID data is not already stored in the remote DSN memory. As anotherexample, the processing module does not send the newly created encodeddata slices to the remote DSN memory for storage when the processingmodule determines that the RAID data is already stored in the remote DSNmemory. Note that the alternative described above may provide a memoryutilization efficiency improvement within the remote DSN memory.

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “operably coupled to”, “coupled to”, and/or “coupling” includesdirect coupling between items and/or indirect coupling between items viaan intervening item (e.g., an item includes, but is not limited to, acomponent, an element, a circuit, and/or a module) where, for indirectcoupling, the intervening item does not modify the information of asignal but may adjust its current level, voltage level, and/or powerlevel. As may further be used herein, inferred coupling (i.e., where oneelement is coupled to another element by inference) includes direct andindirect coupling between two items in the same manner as “coupled to”.As may even further be used herein, the term “operable to” or “operablycoupled to” indicates that an item includes one or more of powerconnections, input(s), output(s), etc., to perform, when activated, oneor more its corresponding functions and may further include inferredcoupling to one or more other items. As may still further be usedherein, the term “associated with”, includes direct and/or indirectcoupling of separate items and/or one item being embedded within anotheritem. As may be used herein, the term “compares favorably”, indicatesthat a comparison between two or more items, signals, etc., provides adesired relationship. For example, when the desired relationship is thatsignal 1 has a greater magnitude than signal 2, a favorable comparisonmay be achieved when the magnitude of signal 1 is greater than that ofsignal 2 or when the magnitude of signal 2 is less than that of signal1.

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention.

The present invention has been described, at least in part, in terms ofone or more embodiments. An embodiment of the present invention is usedherein to illustrate the present invention, an aspect thereof, a featurethereof, a concept thereof, and/or an example thereof. A physicalembodiment of an apparatus, an article of manufacture, a machine, and/orof a process that embodies the present invention may include one or moreof the aspects, features, concepts, examples, etc. described withreference to one or more of the embodiments discussed herein.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of certainsignificant functions. The boundaries of these functional buildingblocks have been arbitrarily defined for convenience of description.Alternate boundaries could be defined as long as the certain significantfunctions are appropriately performed. Similarly, flow diagram blocksmay also have been arbitrarily defined herein to illustrate certainsignificant functionality. To the extent used, the flow diagram blockboundaries and sequence could have been defined otherwise and stillperform the certain significant functionality. Such alternatedefinitions of both functional building blocks and flow diagram blocksand sequences are thus within the scope and spirit of the claimedinvention. One of average skill in the art will also recognize that thefunctional building blocks, and other illustrative blocks, modules andcomponents herein, can be implemented as illustrated or by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or any combination thereof.

What is claimed is:
 1. A method for execution by a processing module ina distributed storage (DS) unit, the method comprising: receiving arequest to retrieve data; identifying a set of redundant array ofindependent disks (RAID) data blocks and corresponding RAID parityblocks that correspond to the data within RAID memory; when the set ofRAID data blocks is error-free: retrieving the data based on the set ofRAID data blocks; and outputting, via a communication interface of theDS unit, the data based on the set of RAID data blocks; and when the setof RAID data blocks includes more errors than are correctable based onthe RAID parity blocks: retrieving the data based on a backup copy ofthe data from a dispersed storage network (DSN) memory, wherein thebackup copy of the data is stored in the DSN memory as one or more setsof encoded data slices; and outputting, via the communication interfaceof the DS unit, the data based on the backup copy of the data.
 2. Themethod of claim 1 further comprising: when the set of RAID data blocksincludes more errors than are correctable based on the RAID parityblocks: generating a copy of the set of RAID data blocks based on thebackup copy of the data; and outputting, via the communication interfaceof the DS unit, the copy of the set of RAID data blocks.
 3. The methodof claim 1 further comprising: when the set of RAID data blocks includesmore errors than are correctable based on the RAID parity blocks:generating a copy of the set of RAID data blocks based on the backupcopy of the data; and transmitting, via the communication interface ofthe DS unit, a store command accompanied with the copy of the set ofRAID data blocks to the RAID memory.
 4. The method of claim 1, wherein:other data is stored within the DSN memory based on first distributeddata storage parameters; and the backup copy of the data is storedwithin the DSN memory based on second distributed data storageparameters that are relatively less reliable or have relatively lesserror correcting capability than the first distributed data storageparameters.
 5. The method of claim 1 further comprising: calculatingother RAID parity blocks based on the set of RAID data blocks; comparingthe other RAID parity blocks with the RAID parity blocks; determiningthat the set of RAID data blocks is error-free when the other RAIDparity blocks compare favorably with the RAID parity blocks; anddetermining that the set of RAID data blocks includes one or more errorswhen the other RAID parity blocks compare unfavorably with the RAIDparity blocks.
 6. The method of claim 1 further comprising: when the setof RAID data blocks includes the more errors than are correctable basedon the RAID parity blocks: retrieving a decode threshold number of errorcoded (EC) data slices of a set of EC data slices from the DSN memory,wherein a data segment of the backup copy of the data is dispersed errorencoded to produce the set of EC data slices; reconstructing the datasegment of the backup copy of the data using the decode threshold numberof EC data slices; and reconstructing the backup copy of the data usingthe data segment.
 7. The method of claim 1, wherein the DSN memory islocal DSN memory that is located within local proximity to the DS unit.8. The method of claim 1, wherein the DSN memory is remote DSN memorythat is included within another at least one DS unit that is locatedoutside of local proximity to the DS unit.
 9. A distributed storage (DS)processing unit comprises: a communication interface; and a processingmodule configured to: receive a request to retrieve data; identify a setof redundant array of independent disks (RAID) data blocks andcorresponding RAID parity blocks that correspond to the data within RAIDmemory; and when the set of RAID data blocks is error-free: retrieve thedata based on the set of RAID data blocks; and output, via thecommunication interface, the data based on the set of RAID data blocks;and when the set of RAID data blocks includes more errors than arecorrectable based on the RAID parity blocks: retrieve the data based ona backup copy of the data from a dispersed storage network (DSN) memory,wherein the backup copy of the data is stored in the DSN memory as oneor more sets of encoded data slices; and output, via the communicationinterface, the data based on the backup copy of the data.
 10. The DSprocessing unit of claim 9, wherein the processing module is furtherconfigured, when the set of RAID data blocks includes more errors thanare correctable based on the RAID parity blocks, to: generate a copy ofthe set of RAID data blocks based on the backup copy of the data; andoutput, via the communication interface of the DS unit, the copy of theset of RAID data blocks.
 11. The DS processing unit of claim 9, whereinthe processing module is further configured, when the set of RAID datablocks includes more errors than are correctable based on the RAIDparity blocks, to: generate a copy of the set of RAID data blocks basedon the backup copy of the data; and transmit, via the communicationinterface of the DS unit, a store command accompanied with the copy ofthe set of RAID data blocks to the RAID memory.
 12. The DS processingunit of claim 9, wherein: other data is stored within the DSN memorybased on first distributed data storage parameters; and the backup copyof the data is stored within the DSN memory based on second distributeddata storage parameters that are relatively less reliable or haverelatively less error correcting capability than the first distributeddata storage parameters.
 13. The DS processing unit of claim 9, whereinthe processing module is further configured to: calculate other RAIDparity blocks based on the set of RAID data blocks; compare the otherRAID parity blocks with the RAID parity blocks; determine that the setof RAID data blocks is error-free when the other RAID parity blockscompare favorably with the RAID parity blocks; and determine that theset of RAID data blocks includes one or more errors when the other RAIDparity blocks compare unfavorably with the RAID parity blocks.
 14. TheDS processing unit of claim 9, wherein the processing module is furtherconfigured, when the set of RAID data blocks includes the more errorsthan are correctable based on the RAID parity blocks, to: retrieve adecode threshold number of error coded (EC) data slices of a set of ECdata slices from the DSN memory, wherein a data segment of the backupcopy of the data is dispersed error encoded to produce the set of ECdata slices; reconstruct the data segment of the backup copy of the datausing the decode threshold number of EC data slices; and reconstruct thebackup copy of the data using the data segment.
 15. The DS processingunit of claim 9, wherein the DSN memory is local DSN memory that islocated within local proximity to the DS unit.
 16. The DS processingunit of claim 9, wherein the DSN memory is remote DSN memory that isincluded within another at least one DS unit that is located outside oflocal proximity to the DS unit.
 17. A computer readable medium havinginstructions causing a processing module in a distributed storage (DS)unit to execute a method comprising: receiving a request to retrievedata; identifying a set of redundant array of independent disks (RAID)data blocks and corresponding RAID parity blocks that correspond to thedata within RAID memory; when the set of RAID data blocks is error-free:retrieving the data based on the set of RAID data blocks; andoutputting, via a communication interface of the DS unit, the data basedon the set of RAID data blocks; and when the set of RAID data blocksincludes more errors than are correctable based on the RAID parityblocks: retrieving the data based on a backup copy of the data from adispersed storage network (DSN) memory, wherein the backup copy of thedata is stored in the DSN memory as one or more sets of encoded dataslices; and outputting, via the communication interface of the DS unit,the data based on the backup copy of the data.
 18. The computer readablemedium having instructions causing the processing module to execute themethod of claim 17 further comprising: when the set of RAID data blocksincludes more errors than are correctable based on the RAID parityblocks: generating a copy of the set of RAID data blocks based on thebackup copy of the data; and outputting, via the communication interfaceof the DS unit, the copy of the set of RAID data blocks.
 19. Thecomputer readable medium having instructions causing the processingmodule to execute the method of claim 17 further comprising: when theset of RAID data blocks includes more errors than are correctable basedon the RAID parity blocks: generating a copy of the set of RAID datablocks based on the backup copy of the data; and transmitting, via thecommunication interface of the DS unit, a store command accompanied withthe copy of the set of RAID data blocks to the RAID memory.
 20. Thecomputer readable medium having instructions causing the processingmodule to execute the method of claim 17, wherein: other data is storedwithin the DSN memory based on first distributed data storageparameters; and the backup copy of the data is stored within the DSNmemory based on second distributed data storage parameters that arerelatively less reliable or have relatively less error correctingcapability than the first distributed data storage parameters.
 21. Thecomputer readable medium having instructions causing the processingmodule to execute the method of claim 17 further comprising: calculatingother RAID parity blocks based on the set of RAID data blocks; comparingthe other RAID parity blocks with the RAID parity blocks; determiningthat the set of RAID data blocks is error-free when the other RAIDparity blocks compare favorably with the RAID parity blocks; anddetermining that the set of RAID data blocks includes one or more errorswhen the other RAID parity blocks compare unfavorably with the RAIDparity blocks.
 22. The computer readable medium having instructionscausing the processing module to execute the method of claim 17 furthercomprising: when the set of RAID data blocks includes the more errorsthan are correctable based on the RAID parity blocks: retrieving adecode threshold number of error coded (EC) data slices of a set of ECdata slices from the DSN memory, wherein a data segment of the backupcopy of the data is dispersed error encoded to produce the set of ECdata slices; reconstructing the data segment of the backup copy of thedata using the decode threshold number of EC data slices; andreconstructing the backup copy of the data using the data segment. 23.The computer readable medium having instructions causing the processingmodule to execute the method of claim 17, wherein the DSN memory islocal DSN memory that is located within local proximity to the DS unit.24. The computer readable medium having instructions causing theprocessing module to execute the method of claim 17, wherein the DSNmemory is remote DSN memory that is included within another at least oneDS unit that is located outside of local proximity to the DS unit.